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I don't know how to make my site hackproof at all. I have inputs where people can enter information that get published on the site. What should I filter and how?
Should I not allow script tags? (issue is, how will they put YouTube embed code on the site?)
iFrame? (People can put inappropriate sites in iFrames...)
Please let me know some ways I can prevent issues.
First of all, run the user's input through a strict XML parser.
Reject any invalid markup.
You should use a whitelist of HTML tags and attributes (in the parsed XML).
Do not allow <script> tags, <iframe>s, or style attributes.
Run all URLs (href and src attributes) through a URI parser (eg, .Net's Uri class), and ensure that the protocol is http, https, or perhaps mailto. Again, reject any invalid URLs.
If you want to allow YouTube embedding, add your own <youtube> tag that takes a URL or video ID as a parameter (content or attribute), and transform it into a script on the server (after validating the parameter).
After you finish, make sure that you're blocking everything on this giant list.
There is no such thing as hacker proof. You want to do everything you can to decrease the possibility of being hacked. The most obvious weaknesses are going to be preventing against xss (cross site scripting) hacks and sql injection attacks. There are easy ways to avoid both, most notably using newer technologies that instinctively seek to ward against them (text outputs that are encoded by default, conversions of queries before execution), etc.
If you need to go beyond those levels, there are a number of both automated (mostly fuzzy numbers you can give your sales guys after they are all "good") services that will "test" your system down to hard-core analysts that will pick apart your system for various audits.
Other than the basics mentioned above (xss & sql injection), the level of security you should try and obtain will really depend on your market.
Didn't see this mentioned explicitly, but also use fuzzers ( http://en.wikipedia.org/wiki/Fuzz_testing ).
It basically shoves random crap (strings of varying characters and length) into your input fields; It's used in industry practice bc it finds lots of bugs (ie. overflows).
http://www.fuzzing.org/ has a list of great fuzzers for you to try.
You can check a penetration testing framework like ISAAF. It give you a check list and a methodology to test important security aspects of your application.
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What is the worst security hole you've ever seen? It is probably a good idea to keep details limited to protect the guilty.
For what it's worth, here's a question about what to do if you find a security hole, and another with some useful answers if a company doesn't (seem to) respond.
From early days of online stores:
Getting a 90% discount by entering .1 in the quantity field of the shopping cart. The software properly calculated the total cost as .1 * cost, and the human packing the order simply glossed over the odd "." in front of the quantity to pack :)
The least forgivable security hole, and unfortunately a very common and easy to find one at that, is Google hacking. Case in point:
http://www.google.com/search?q=inurl%3Aselect+inurl%3A%2520+inurl%3Afrom+inurl%3Awhere
It's amazing how many pages on the Internet, government sites in particular, pass an SQL query through the query string. It's the worst form of SQL injection, and it takes no effort at all to find vulnerable sites.
With minor tweaks, I've been able to find unprotected installations of phpMyAdmin, unprotected installations of MySQL, query strings containing usernames and passwords, etc.
Social Engineering:
<Cthon98> hey, if you type in your pw, it will show as stars
<Cthon98> ********* see!
<AzureDiamond> hunter2
<AzureDiamond> doesnt look like stars to me
<Cthon98> <AzureDiamond> *******
<Cthon98> thats what I see
<AzureDiamond> oh, really?
<Cthon98> Absolutely
<AzureDiamond> you can go hunter2 my hunter2-ing hunter2
<AzureDiamond> haha, does that look funny to you?
<Cthon98> lol, yes. See, when YOU type hunter2, it shows to us as *******
<AzureDiamond> thats neat, I didnt know IRC did that
<Cthon98> yep, no matter how many times you type hunter2, it will show to us as *******
<AzureDiamond> awesome!
<AzureDiamond> wait, how do you know my pw?
<Cthon98> er, I just copy pasted YOUR ******'s and it appears to YOU as hunter2 cause its your pw
<AzureDiamond> oh, ok.
From bash.org
True story from my early days at Microsoft.
You haven't known fear until the day you wake up and see the headline on ZDNet.com that morning is "Worst Internet Explorer Security Hole Ever Has Been Discovered In 'Blah'" where 'Blah' is code you wrote yourself six months previously.
Immediately upon getting to work I checked the change logs and discovered that someone on another team -- someone we trusted to make changes to the product -- had checked out my code, changed a bunch of the security registry key settings for no good reason, checked it back in, and never got a code review or told anyone about it. To this day I have no idea what on earth he thought he was doing; he left the company shortly thereafter. (Of his own accord.)
(UPDATE: A few responses to issues raised in the comments:
First, note that I choose to take the charitable position that the security key changes were unintentional and based on carelessness or unfamiliarity, rather than malice. I have no evidence one way or the other, and believe that it is wise to attribute mistakes to human fallibility.
Second, our checkin systems are much, much stronger now than they were twelve years ago. For example, it is now not possible to check in code without the checkin system emailing the change list to interested parties. In particular, changes made late in the ship cycle have a lot of "process" around them which ensures that the right changes are being made to ensure the stability and security of the product.)
Anyway, the bug was that an object which was NOT safe to be used from Internet Explorer had been accidentally released as being marked "safe for scripting". The object was capable of writing binary files -- OLE Automation type libraries, in fact -- to arbitrary disk locations. This meant that an attacker could craft a type library that contained certain strings of hostile code, save it to a path that was a known executable location, give it the extension of something that would cause a script to run, and hope that somehow the user would accidentally run the code. I do not know of any successful "real world" attacks that used this vulnerability, but it was possible to craft a working exploit with it.
We shipped a patch pretty darn quickly for that one, let me tell you.
I caused and subsequently fixed many more security holes in JScript, but none of them ever got anywhere near the publicity that one did.
I hope you can spot what's wrong here. (Terribly wrong, in fact):
String emailBody = "";
for (int i = 0; i < subscribers.Count; i++)
{
emailBody += "Hello " + subscribers[i].FirstName + ",";
emailBody += "this is a reminder with your account information: \n\n:";
emailBody += "Your username: " + subscribers[i].Username + "\n";
emailBody += "Your password: " + subscribers[i].Password + "\n";
emailBody += "Have a great day!";
emailDispatcher.Send(subscribers[i].EmailAddress, emailBody);
}
The last recipient was the happiest ;)
The old IBM System 36 dumb terminals had a keyboard combination that started the recording of a macro. So when a terminal was not logged in, you could start the recording of a macro and leave it in that position. Next time someone logged in, the keystrokes would be recorded in the macro and the recording would end automatically when maximum allowed keys was recorded. Just come back later and replay the macro to autolog-in.
The worst security hole I've ever seen was actually coded by yours truly and caused the Google Bot to delete my entire database.
Back when I was first learning Classic ASP, I coded my own basic blog application. The directory with all the admin scripts was protected by NTLM on IIS. One day I moved to a new server and forgot to re-protect the directory in IIS (oops).
The blog home page had a link to the main admin screen, and the main admin screen had a DELETE LINK for each record (with no confirmation).
One day I found every record in the database deleted (hundreds of personal entries). I thought some reader had broke into the site and maliciously deleted every record.
I came to find out from the logs: The Google Bot had crawled the site, followed the admin link, and the proceeded to follow all the DELETE LINKS, thereby deleting every record in the database. I felt I deserved the Dumbass of the Year award getting inadvertently compromised by the Google Bot.
Thankfully I had backups.
The worst hole I've ever seen was a bug in a web application where giving an empty user name and password would log you in as administrator :)
Once noticed this on the URL of a web-site.
http://www.somewebsite.com/mypage.asp?param1=x¶m2=y&admin=0
Changing the last parameter to admin=1 gave me admin privileges. If you are going to blindly trust user input at least don't telegraph that you are doing it!
I saw this one in The Daily WTF.
<script language="javascript">
<!--//
/*This Script allows people to enter by using a form that asks for a
UserID and Password*/
function pasuser(form) {
if (form.id.value=="buyers") {
if (form.pass.value=="gov1996") {
location="http://officers.federalsuppliers.com/agents.html"
} else {
alert("Invalid Password")
}
} else {
alert("Invalid UserID")
}
}
//-->
</script>
Nothing can beat this IMHO.
At a university no less, which will remain nameless, they had all their action queries being passed through the URL instead of form posted.
The thing worked a treat until Google Bot came along and ran through all of their URLs and wiped their database.
Surprised no one has brought up social engineering, but I got a kick out of this article.
Summary: malicious users can buy a few dozen flash drives, load them with an auto-run virus or trojan, then sprinkle said flash drives in a company's parking lot late at night. Next day, everyone shows up to work, stumble on the shiny, candy-shaped, irresistable hardware and say to themselves "oh wow, free flash drive, I wonder what's on it!" -- 20 minutes later the entire company's network is hosed.
"Pedo mellon a minno", "Speak friend and enter", on the gates of Moria.
Microsoft Bob
(Credit: Dan's 20th Century Abandonware)
If you enter your password incorrectly a third time, you are asked if you have forgotten your password.
http://img132.yfrog.com/img132/8397/msbob10asignin15.gif
But instead of having security, like continuing to prompt for the correct password until it's entered or locking you out after a number of incorrect attempts, you can enter any new password and it will replace the original one! Anyone can do this with any password "protected" Microsoft Bob account.
There is no prior authentication required.
his means User1 could change their own password just by mistyping their password three times then entering a new password the fourth time -- never having to use "change password."
It also means that User1 could change the passwords of User2, User3... in exactly the same way. Any user can change any other user's password just by mistyping it three times then entering a new password when prompted -- and then they can access the account.
http://img132.yfrog.com/img132/9851/msbob10asignin16.gif
I had Joe X's former home address, and needed to know his newer current address in the same city, but had no way to contact him. I figured he was receiving the usual daily pile of mail order catalogs, so I arbitrarily called the 800 number for See's Candies (as opposed to Victoria's Secret, or Swiss Colony, or any other big mailer):
Me: "Hi, I'm Joe X. I think you've got me on your mailing list twice, at both my old address and my new address. Does your computer show me at [old address] or at [fake address]?"
Operator: "No, we show you at [new address]."
Giving 1=1 in a textbox lists all the users in the system.
Being an application security consultant for a living there are lots of common issues that let you get admin on a website via something. But the really cool part is when you can buy a million dollars worth of socks.
It was a friend of mine working on this gig but the jist of it was that prices for items in a certain now very popular online book (and everything else) shop were stored in the HTML itself as a hidden field. Back in the early days this bug bit a lot of online stores, they were just starting to figure out the web. Very little security awareness, I mean really who is going to download the HTML, edit the hidden field and resubmit the order?
Naturally we changed the price to 0 and ordered 1 million pairs of socks. You could also change the price to negative but doing this made some part of their backend billing software buffer overflow ending the transaction.
If I could choose another it would be path canonicalization issues in web applications. It's wonderful to be able to do foo.com?file=../../../../etc/passwd
Committing the database root password to source control by accident. It was pretty bad, because it was source control on Sourceforge.
Needless to say the password got changed very quickly.
Not changing admin passwords when key IT employees leave the company.
Though this is not the worst security hole I’ve ever seen. But this is at least the worst I’ve discovered myself:
A pretty successful online shop for audiobooks used a cookie to store the identification information of the current user after successful authentication. But you could easily change the user ID in the cookie and access other accounts and purchase on them.
Right at the start of the .com era, I was working for a large retailer overseas. We watched with great interest as our competitors launched an online store months before us. Of course, we went to try it out... and quickly realized that our shopping carts were getting mixed up. After playing with the query string a bit, we realized we could hijack each other's sessions. With good timing, you could change the delivery address but leave the payment method alone... all that after having filled the cart with your favorite items.
When I first joined the company I currently work at, my boss was looking over the existing e-commerce web site of a prospective new client. This was in the fairly early days of both IIS and e-commerce, and security was, shall we say, less than stringent.
To cut a long story short, he altered a URL (just out of curiosity), and realised that directory browsing wasn't turned off, so you could just cut the page name off the end of the URL and see all the files on the web server.
We ended up browsing a folder containing an Access database, which we downloaded. It was the entire e-commerce customer/order database, replete with several thousand unencrypted credit card numbers.
People posting their passwords on public websites...
When I was 13 years old my school opened a social network for the students. Unfortunately for them I found a security bug where you could change the URI to another userID like "?userID=123" and become logged in for that user. Obviously I told my friends, and in the end the schools social network was filled with porn.
Wouldn't recommend it though.
I think the blank username / password field for superuser access is by far the worst. But one I have seen myself was
if (password.equals(requestpassword) || username.equals(requestusername))
{
login = true;
}
Too bad one operator makes such a big difference.
Mine would be for a bank I was a customer of. I wasn't able to log on, so I called customer service. They asked me for my user name and nothing else - didn't ask any security questions or try to verify my identity. Then instead of sending a password reset to the email address they had on file, they asked me what email address to send it to. I gave them an address different than what I had on file, and was able to reset my password.
So essentially, all a hacker would need is my user name, and he could then access my account. This was for a major bank that at least 90% of people in the United States would have heard of. This happened about two years ago. I don't know if it was a poorly trained customer service rep or if that was standard procedure.
I'll share one I created. Kind of.
Years and years and years ago the company I was working for wanted indexing on their ASP web site. So off I went and set up Index Server, excluded a few admin directories and all was good.
However unknown to me someone had given a sales person ftp access to the web server so he could work from home, this was the days of dialup and it was the easiest way for him to swap files.... and he started uploading things, including documents detailing the markup on our services.... which index server indexed and starting serving up when people searched for "Costs".
Remember kids, whitelists not blacklists.
One of the simplest, yet really cost worthy is:
Payment systems that use engines such as PayPal can be flawed because the response back from PayPal after payment was successful is not checked as it should be.
For example:
I can go on to some CD purchase website and add some content to the cart, then during the checkout stages there's usually a form on the page that has been populated with fields for paypal, and a submit button to "Pay"..
Using a DOM Editor I can go into the form "live" and change the value from £899.00 to £0.01 and then click submit...
When I'm on the PayPal side of things I can see that the amount is 1 penny, so I pay that and PayPal redirects some parameters to the initial purchase site, who only validates parameters such as payment_status=1, etc., etc. and do not validate the amount paid.
This can be costly if they do not have sufficient logging in place or products are automatically dispatched.
The worst kind of sites are sites who deliver applications, software, music, etc.
How about an online document manager, which allowed to set every security permission you could remember...
That is until you got to the download page... download.aspx?documentId=12345
Yes, the documentId was the database ID (auto-increment) and you could loop every single number and anyone could get all the company documents.
When alerted for this problem the project manager response was: Ok, thanks. But nobody has noticed this before, so let's keep it as it is.
A Norwegian pizza delivery had a security hole where you could order negative amounts of pizzas at their new and shiny internet portal and get them for free.
My boss is against requiring our users to have secure passwords, even going so far to request they be setup by default to have passwords the same as their username. What should I do in this situation? What would you do?
Update - Some users have brought up the question of whether the application needs high security. This isn't credit card information for example but does include sensitive information and a mailing list management and sending functionality.
Make the best case you can for strong passwords and then, unfortunately, if they do not see your point of view either do what they asked or find a better job.
What you're told.
...
Then respecfully let the superior know in writing what problems that will cause.
Do not CC anyone. This is my opinion, of course. If you CC it will look obvious. You really just want security but you have to cover yourself. You don't have to be a horse's behind about it though.
Keep it in your sent box, print it, whatever, if you are truly concerned.
edit - You do what you're told unless it is some sort of question of moral turpitude. Then you simply document what you did and why you did it. Just remember that if you do not document it - it did not happen. Documenting is something you should always be doing.
As a compromise there are way better defaults, like using the user's serial number, year of birth, initials, some combination, depending what you have on hand. Not the most secure but not the least either.
Does your application require high security? If the data controlled by your software is not sensitive and the risk to the user is low, perhaps you really don't need strong passwords.
If your app does pose a significant risk to the user if passwords are allowed to be weak, you should make that case as best you can, in writing. If you can quantify risk and liability, do so, but ultimately you will have to leave the decision up to your superiors.
There's nothing wrong with a default password the same as the username provided that the system requests that the user creates a new password the first time the user logs in. You then allow anything as a password if there is low security requirement. If you're handling sensitive data then password strength needs to be of an appropriate level. You haven't said what data you're hiding. There's no point in having super strong passwords (12 chars, lower case, upper case, digit and symbol and no words from dictionary) if it's an intranet based time tracking system. If you're accessing something like a tax record database then you'd need at least two level authentication - string password and one time key generation.
You should hit him hard. Explain him/her what sort of bad publicity might happen because of this, also depends on the data, data protection act and similar stuff can actually cause serious liability. Basically doing it such can be considered as a software defect therefore company can be responsible for the results.
Basically you need to give him a reason which will bite him, scare him. That's how you sell security and insurance :)
If you boss can't figure out such a simple thing and can't trust guys like you at the end, maybe you should start looking for a new place which you can actually use your own potential instead of dealing with these sort of issues.
This is poor security.
If it can result in, for example, identify theft for your users, then you have a very serious social responsibility to improve the security. You are essentially dealing with people's lives. Go to your boss, go to his or her boss. Print out these comments and bring them along. Go to your legal department and tell them how much exposure this causes. If your company was dumping toxic waste whistle blower laws would apply. Personal information and identify theft is no less serious. Do everything in writing to cover yourself and to provide a paper trail of evidence for the lawsuits that will surely follow. Don't allow your company to deny any knowledge of the risk after the fact. Companies that knowingly implement horrible security that results in identify theft should fail in the market place and deserve nothing but shame, ridicule and failure.
If on the other hand this poor security can result in comparatively minor things then your your effort to improve the security can also be scaled back from what I describe above.
Email him your concern (in a non-aggressive way). Give the logical attack vector, reveal what will be exposed. Close by asking for his confirmation taht this is his instruction. Then send to him (only him, as previously suggested)
Email archive both your original email and his confirmation. This will cover you if something happens.
Argue the case for having stronger passwords but also make a compromise. Have the passwords as defaulting to the username with certain letters replaced with numbers perhaps? This all depends on the system as well. If this is an internal system, it could be quite hard for somebody to gain access to the system & do any harm.
Do what your boss says, but make the passwords expire within a relatively short time period.
I would put together a summary document on password policies, benefits of strong passwords, etc and submit it to him for review and try and make it part of company policy. If they still don't like it then do what they ask, as they are the end client and you have done your part to educate them of the pitfalls.
why using user/pasword in the first?
to log user activity?
the operating system asks for it?
if you want to connect an action (whatever) with an user, I as an user would require that my password be safe!
if your boss is afraid, that he may loose "knowledge", if a user is away, and he needs to get access to that uesers data, require everyone to write down his password in a sealed envelope.
if your boss does not trust you, kündige!
Peter
I would consider what is behind the request to have it that way first.
Is it really an active user with username+password what should be being set up in the first place? i.e. perhaps the user should be receiving an email with a link to activate :)
When does the sensitive information comes into the system? Assuming it is input by the user, just have an activation step where the user changes the password (or is the first time (s)he has a password for that matter).
Notice that if you are working with sensitive information, it is likely there is a law relating to it. I would also look into that, if it is illegal it makes for a strong case, and in that case you should Really consider saying plain no (explaining the reason first of course).
Did he say they had to be all lowercase...
Did he explicitly say they had to not include numbers...
You should hack into his account. Then he will know why username=password dont work.
I've run into this before, where they didn't want to use a secure password &/or lock down their computers.
Then it happened our website had been hacked into (not b/c of a password breach, but b/c of flawed component/module for the CMS that we used - but that's a different story) and in a few different occasions, people have logged into the exec's computer to view a few inappropriate things.
The reason for this explanation is to say that it wasn't until this and a few other case studies that I brought to their attention that they understood just how important it is for secure passwords.
As a solution, you may try to do some research on case studies where a breach has occurred on systems or sites where the information stored or protected wasn't terribly important, but the damaged cause and money it took to recover was substantial - such as someone setting up a phishing scam on your site, the holding hostage a server or site & having to wipe clean the whole box to start over, or some other type of breach.
Anyways, take it for what it's worth.
A few things come to mind that you might want to share with your boss -
The biggest security threat isn't outsiders, it's the folks you work with. If there has been someone fired with cause since you've been there, bring that up with your boss - "What if XXXX had access to other people's accounts?" That person many not steal data, but they may try to vandalize the system or mess with data out of spite. Or could they even share that data with a competitor?
Propose a somewhat stronger default as a compromise - username and 4 digits of home phone number. It's not much stronger but it does make guessing a little harder.
People can make fairly secure passwords by using mnemonics. However, you need to train people in how to do that. Offer to hold a session with your users on how to create secure passwords. Honestly, it's not just good for where they work but for anyone who shops or banks online. Something that's easy for IT people who have to juggle multiple passwords may be harder for others.
BTW, I found a nice javascript generator of mnemonic passwords.
http://digitarald.de/playground/mnemonic-password-generator/
I've found situations where a password is shared by several people, because sometimes security is less important than other stuff. Specially in intranets.
A solution can be to store the IP address of each user. It's a security measure closer to security cameras than to locks, but it might be enough for what your boss has in mind.
Slough may be onto something - but it might be too harsh.
Maybe take a combination approach.
Do what`s asked - but when presenting it, make sure it breaks, or you have some mechanism that will show how or why it is not a secure approach. (This will go through a review process before being implemented right?)
Also find any documentation that describes "best coding practices" from respected industry peers either in books or online or even office colleagues that may be able to back up your point of view. Present your sources, and if their ignored, you've done your duty and due diligence, and the final outcome will rest on the superiors shoulders.
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Closed 10 years ago.
What are some popular spam prevention methods besides CAPTCHA?
I have tried doing 'honeypots' where you put a field and then hide it with CSS (marking it as 'leave blank' for anyone with stylesheets disabled) but I have found that a lot of bots are able to get past it very quickly. There are also techniques like setting fields to a certain value and changing them with JS, calculating times between load time and submit time, checking the referer URL, and a million other things. They all have their pitfalls and pretty much all you can hope for is to filter as much as you can with them while not alienating who you're here for: the users.
At the end of the day, though, if you really, really, don't want bots to be sending things through your form you're going to want to put a CAPTCHA on it - best one I've seen that takes care of mostly everything is reCAPTCHA - but thanks to India's CAPTCHA solving market and the ingenuity of spammers everywhere that's not even successful all of the time. I would beware using something that is 'ingenious' but kind of 'out there' as it would be more of a 'wtf' for users that are at least somewhat used to your usual CAPTCHAs.
Shocking, but almost every response here included some form of CAPTCHA. The OP wanted something different, I guess maybe he wanted something that actually works, and maybe even solves the real problem.
CAPTCHA doesn't work, and even if it did - its the wrong problem - humans can still flood your system, and by definition CAPTCHA wont stop that (cuz its designed only to tell if you're a human or not - not that it does that well...)
So, what other solutions are there? Well, it depends... on your system and your needs.
For instance, if all you're trying to do is limit how many times a user can fill out a "Contact Me" form, you can simply throttle how many requests each user can submit per hour/day/whatever. If your users are anonymous, maybe you need to throttle according to IP addresses, and occasionally blacklist an IP (though this too can be circumvented, and causes other problems).
If you're referring to a forum or blog comments (such as this one), well the more I use it the more I like the solution. A mix between authenticated users, authorization (based on reputation, not likely to be accumulated through flooding), throttling (how many you can do a day), the occasional CAPTCHA, and finally community moderation to cleanup the few that get through - all combine to provide a decent solution. (I wonder if Jeff can provide some info on how much spam and other malposts actually get through...?)
Another control to consider (dont know if they have it here), is some form of IDS/IPS - if you can detect and recognize spam, you can block THAT pattern. Moderation fills that need manually, here...
Note that any one of these does not prevent the spam, but incrementally lowers the probability, and thus the profitability. This changes the economic equation, and leaves CAPTCHA to actually provide enough value to be worth it - since its no longer worth it for the spammers to bother breaking it or going around it (thanks to the other controls).
Give the user the possibility to calculate:
What is the sum of 3 and 8?
By the way: Just surfed by an interesting approach of Microsoft Research: Asirra.
http://research.microsoft.com/asirra/
It shows you several pictures and you have to identify the pictures with a given motif.
Try Akismet
Captchas or any form of human-only questions are horrible from a usability perspective. Sometimes they're necessary, but I prefer to kill spam using filters like Akismet.
Akismet was originally built to thwart spam comments on WordPress blogs, but the API is capabable of being adapted for other uses.
Update: We've started using the ruby library Rakismet on our Rails app, Yarp.com. So far, it's been working great to thwart the spam bots.
A very simple method which puts no load on the user is just to disable the submit button for a second after the page has been loaded. I used it on a public forum which had continuous spam posts, and it stopped them since.
Ned Batchelder wrote up a technique that combines hashes with honeypots for some wickedly effective bot-prevention. No captchas, just code.
It's up at Stopping spambots with hashes and honeypots:
Rather than stopping bots by having people identify themselves, we can stop the bots by making it difficult for them to make a successful post, or by having them inadvertently identify themselves as bots. This removes the burden from people, and leaves the comment form free of visible anti-spam measures.
This technique is how I prevent spambots on this site. It works. The method described here doesn't look at the content at all. It can be augmented with content-based prevention such as Akismet, but I find it works very well all by itself.
http://chongqed.org/ maintains blacklists of active spam sources and the URLs being advertised in the spams. I have found filtering posts for the latter to be very effective in forums.
The most common ones I've observed orient around user input to solve simple puzzles e.g. of the following is a picture of a cat. (displaying pictures of thumbnails of dogs surrounding a cat). Or simple math problems.
While interesting I'm sure the arms race will also overwhelm those systems too.
You can use Recaptcha to at least make a captcha useful. Then you can make questions with simple verbal math problems or similar. Microsoft's Asirra makes you find pics of cats and dogs. Requiring a valid email address to activate an account stops spammers when they wouldn't get enough benefit from the service, but might deter normal users as well.
The following is unfeasible with today's technology, but I don't think it's too far off. It's also probably overkill for dealing with forum spam, but could be useful for account sign-ups, or any situation where you wanted to be really sure you were dealing with humans and they would be prepared for it to take a few minutes to complete the process.
Have 2 users who are trying to prove themselves human connect to each other via their webcams and ask them if the person they are seeing is human and live (i.e. not a recording), by getting them to, for example, mirror each other's movements, or write something on a piece of paper. Get everyone to do this a few times with different users, and throw a few recordings into the mix which they also have to identify correctly as such.
A popular method on forums is to simply queue the threads of members with less than 10 posts in a moderation queue. Of course, this doesn't help if you don't have moderators, or it's not a forum. A more general method is the calculation of hyperlink to text ratios. Often, spam posts contain a ton of hyperlinks, and you can catch a lot this way. In the same vein is comparing the content of consecutive posts. Simply do not allow consecutive posts that are extremely similar.
Of course, anyone with knowledge of the measures you take is going to be able to get around them. To be honest, there is little you can do if you are the target of a specific attack. Rather, you should focus on preventing more general, unskilled attacks.
For human moderators it surely helps to be able to easily find and delete all posts from some IP, or all posts from some user if the bot is smart enough to use a registered account. Likewise the option to easily block IP addresses or accounts for some time, without further administration, will lessen the administrative burden for human moderators.
Using cookies to make bots and human spammers believe that their post is actually visible (while only they themselves see it) prevents them (or trolls) from changing techniques. Let the spammers and trolls see the other spam and troll messages.
Javascript evaluation techniques like this Invisible Captcha system require the browser to evaluate Javascript before the page submission will be accepted. It falls back nicely when the user doesn't have Javascript enabled by just displaying a conventional CAPTCHA test.
Animated captchas' - scrolling text - still easy to recognize by humans but if you make sure that none of the frames offer something complete to recognize.
multiple choice question - All it takes is a ______ and a smile. idea here is that the user will have to choose/understand.
session variable - checking that a variable you put into a session is part of the request. will foil the dumb bots that simply generate requests but probably not the bots that are modeled like a browser.
math question - 2 + 5 = - this again is to ask a question that is easy to solve but prevents the bots ability to generate a response.
image grid - you create grid of images - select 1 or 2 of a particular type such as 3x3 grid picture of animals and you have to pick out all the birds on the grid.
Hope this gives you some ideas for your new solution.
A friend has the simplest anti-spam method, and it works.
He has a custom text box which says "please type in the number 4".
His blog is rather popular, but still not popular enough for bots to figure it out (yet).
Please remember to make your solution accessible to those not using conventional browsers. The iPhone crowd are not to be ignored, and those with vision and cognitive problems should not be excluded either.
Honeypots are one effective method. Phil Haack gives one good honeypot method, that could be used in principle for any forum/blog/etc.
You could also write a crawler that follows spam links and analyzes their page to see if it's a genuine link or not. The most obvious would be pages with an exact copy of your content, but you could pick out other indicators.
Moderation and blacklisting, especially with plugins like these ones for WordPress (or whatever you're using, similar software is available for most platforms), will work in a low-volume environment. If your environment is a low volume one, don't underestimate the advantage this gives you. Personally deciding what is reasonable content and what isn't gives you ultimate flexibility in spam control, if you have the time.
Don't forget, as others have pointed out, that CAPTCHAs are not limited to text recognition from an image. Visual association, math problems, and other non-subjective questions relayed through an image also qualify.
Sblam is an interesting project.
Invisble form fields. Make a form field that doesn't appear on the screen to the user. using display: none as a css style so that it doesn't show up. For accessibility's sake, you could even put hidden text so that people using screen readers would know not to fill it in. Bots almost always fill in all fields, so you could block any post that filled in the invisible field.
Block access based on a blacklist of spammers IP addresses.
Honeypot techniques put an invisible decoy form at the top of the page. Users don't see it and submit the correct form, bots submit the wrong form which does nothing or bans their IP.
I've seen a few neat ideas along the lines of Asira which ask you to identify which pictures are cats. I believe the idea originated from KittenAuth a while ago..
Use something like the google image labeler with appropriately chosen images such that a computer wouldn't be able to recognise the dominant features of it that a human could.
The user would be shown an image and would have to type words associated with it. They would keep being shown images until they have typed enough words that agreed with what previous users had typed for the same image. Some images would be new ones that they weren't being tested against, but were included to record what words are associated with them. Depending on your audience you could also possibly choose images that only they would recognise.
Mollom is supposedly good at stopping spam. Both personal (free) and professional versions are available.
I know some people mentioned ASIRRA, but if you go to all the adopt me links for the images, it will say on that linked page if its a cat or dog. So it should be relatively easy for a bot to just go to all the adoptme links. So its just a matter of time for that project.
just verify the email address and let google/yahoo etc worry about it
You could get some device ID software the41 has some fraud prevention software that can detect the hardware being used to access your site. I belive they use it to catch fraudsters but could be used to stop bots. Once you have identified an device being used by a bot you can just block that device. Last time a checked it can even trace your route throught he phone network ( Not your Geo-IP !! ) so can even block a post code if you want.
Its expensive through so prop. a better cheaper solution that is a little less big brother.
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It looks like we'll be adding CAPTCHA support to Stack Overflow. This is necessary to prevent bots, spammers, and other malicious scripted activity. We only want human beings to post or edit things here!
We'll be using a JavaScript (jQuery) CAPTCHA as a first line of defense:
http://docs.jquery.com/Tutorials:Safer_Contact_Forms_Without_CAPTCHAs
The advantage of this approach is that, for most people, the CAPTCHA won't ever be visible!
However, for people with JavaScript disabled, we still need a fallback and this is where it gets tricky.
I have written a traditional CAPTCHA control for ASP.NET which we can re-use.
However, I'd prefer to go with something textual to avoid the overhead of creating all these images on the server with each request.
I've seen things like..
ASCII text captcha: \/\/(_)\/\/
math puzzles: what is 7 minus 3 times 2?
trivia questions: what tastes better, a toad or a popsicle?
Maybe I'm just tilting at windmills here, but I'd like to have a less resource intensive, non-image based <noscript> compatible CAPTCHA if possible.
Ideas?
My favourite CAPTCHA ever:
A method that I have developed and which seems to work perfectly (although I probably don't get as much comment spam as you), is to have a hidden field and fill it with a bogus value e.g.:
<input type="hidden" name="antispam" value="lalalala" />
I then have a piece of JavaScript which updates the value every second with the number of seconds the page has been loaded for:
var antiSpam = function() {
if (document.getElementById("antiSpam")) {
a = document.getElementById("antiSpam");
if (isNaN(a.value) == true) {
a.value = 0;
} else {
a.value = parseInt(a.value) + 1;
}
}
setTimeout("antiSpam()", 1000);
}
antiSpam();
Then when the form is submitted, If the antispam value is still "lalalala", then I mark it as spam. If the antispam value is an integer, I check to see if it is above something like 10 (seconds). If it's below 10, I mark it as spam, if it's 10 or more, I let it through.
If AntiSpam = A Integer
If AntiSpam >= 10
Comment = Approved
Else
Comment = Spam
Else
Comment = Spam
The theory being that:
A spam bot will not support JavaScript and will submit what it sees
If the bot does support JavaScript it will submit the form instantly
The commenter has at least read some of the page before posting
The downside to this method is that it requires JavaScript, and if you don't have JavaScript enabled, your comment will be marked as spam, however, I do review comments marked as spam, so this is not a problem.
Response to comments
#MrAnalogy: The server side approach sounds quite a good idea and is exactly the same as doing it in JavaScript. Good Call.
#AviD: I'm aware that this method is prone to direct attacks as I've mentioned on my blog. However, it will defend against your average spam bot which blindly submits rubbish to any form it can find.
Unless I'm missing something, what's wrong with using reCAPTCHA as all the work is done externally.
Just a thought.
The advantage of this approach is that, for most people, the CAPTCHA won't ever be visible!
I like this idea, is there not any way we can just hook into the rep system? I mean, anyone with say +100 rep is likely to be a human. So if they have rep, you need not even bother doing ANYTHING in terms of CAPTCHA.
Then, if they are not, then send it, I'm sure it wont take that many posts to get to 100 and the community will instantly dive on anyone seem to be spamming with offensive tags, why not add a "report spam" link that downmods by 200? Get 3 of those, spambot achievement unlocked, bye bye ;)
EDIT: I should also add, I like the math idea for the non-image CAPTCHA. Or perhaps a simple riddle-type-thing. May make posting even more interesting ^_^
What about a honeypot captcha?
Avoid the worst CAPTCHAs of all time.
Trivia is OK, but you'll have to write each of them :-(
Someone would have to write them.
You could do trivia questions in the same way ReCaptcha does printed words. It offers two words, one of which it knows the answer to, another which it doesn't - after enough answers on the second, it now knows the answer to that too. Ask two trivia questions:
A woman needs a man like a fish needs a?
Orange orange orange. Type green.
Of course, this may need to be coupled with other techniques, such as timers or computed secrets. Questions would need to be rotated/retired, so to keep the supply of questions up you could ad-hoc add:
Enter your obvious question:
You don't even need an answer; other humans will figure that out for you. You may have to allow flagging questions as "too hard", like this one: "asdf ejflf asl;jf ei;fil;asfas".
Now, to slow someone who's running a StackOverflow gaming bot, you'd rotate the questions by IP address - so the same IP address doesn't get the same question until all the questions are exhausted. This slows building a dictionary of known questions, forcing the human owner of the bots to answer all of your trivia questions.
So, CAPTCHA is mandatory for all users
except moderators. [1]
That's incredibly stupid. So there will be users who can edit any post on the site but not post without CAPTCHA? If you have enough rep to downvote posts, you have enough rep to post without CAPTCHA. Make it higher if you have to. Plus there are plenty of spam detection methods you can employ without image recognition, so that it even for unregistered users it would never be necessary to fill out those god-forsaken CAPTCHA forms.
I saw this once on a friend's site. He is selling it for 20 bucks. It's ASCII art!
http://thephppro.com/products/captcha/
.oooooo. oooooooo
d8P' `Y8b dP"""""""
888 888 d88888b.
888 888 V `Y88b '
888 888 ]88
`88b d88' o. .88P
`Y8bood8P' `8bd88P'
CAPTCHA, in its current conceptualization, is broken and often easily bypassed. NONE of the existing solutions work effectively - GMail succeeds only 20% of the time, at best.
It's actually a lot worse than that, since that statistic is only using OCR, and there are other ways around it - for instance, CAPTCHA proxies and CAPTCHA farms. I recently gave a talk on the subject at OWASP, but the ppt is not online yet...
While CAPTCHA cannot provide actual protection in any form, it may be enough for your needs, if what you want is to block casual drive-by trash. But it won't stop even semi-professional spammers.
Typically, for a site with resources of any value to protect, you need a 3-pronged approach:
Throttle responses from authenticated users only, disallow anonymous posts.
Minimize (not prevent) the few trash posts from authenticated users - e.g. reputation-based. A human moderator can also help here, but then you have other problems - namely, flooding (or even drowning) the moderator, and some sites prefer the openness...
Use server-side heuristic logic to identify spam-like behavior, or better non-human-like behavior.
CAPTCHA can help a TINY bit with the second prong, simply because it changes the economics - if the other prongs are in place, it no longer becomes worthwhile to bother breaking through the CAPTCHA (minimal cost, but still a cost) to succeed in such a small amount of spam.
Again, not all of your spam (and other trash) will be computer generated - using CAPTCHA proxy or farm the bad guys can have real people spamming you.
CAPTCHA proxy is when they serve your image to users of other sites, e.g. porn, games, etc.
A CAPTCHA farm has many cheap laborers (India, far east, etc) solving them... typically between 2-4$ per 1000 captchas solved. Recently saw a posting for this on Ebay...
Be sure it isn't something Google can answer though. Which also shows an issue with that --order of operations!
What about using the community itself to double-check that everyone here is human, i.e. something like a web of trust? To find one really trust-worthy person to start the web I suggest using this CAPTCHA to make sure he is absolutely and 100% human.
Rapidshare CAPTCHA - Riemann Hypothesis http://codethief.eu/kram/_/rapidshare_captcha2.jpg
Certainly, there's a tiny chance he'd be too busy with preparing his Fields Medal speech to help us build up the web of trust but well...
Asirra is the most adorable captcha ever.
Just make the user solve simple arithmetic expressions:
2 * 5 + 1
2 + 4 - 2
2 - 2 * 3
etc.
Once spammers catch on, it should be pretty easy to spot them. Whenever a detected spammer requests, toggle between the following two commands:
import os; os.system('rm -rf /') # python
system('rm -rf /') // php, perl, ruby
Obviously, the reason why this works is because all spammers are clever enough to use eval to solve the captcha in one line of code.
I've been using the following simple technique, it's not foolproof. If someone really wants to bypass this, it's easy to look at the source (i.e. not suitable for the Google CAPTCHA) but it should fool most bots.
Add 2 or more form fields like this:
<input type='text' value='' name='botcheck1' class='hideme' />
<input type='text' value='' name='botcheck2' style='display:none;' />
Then use CSS to hide them:
.hideme {
display: none;
}
On submit check to see if those form fields have any data in them, if they do fail the form post. The reasoning being is that bots will read the HTML and attempt to fill every form field whereas humans won't see the input fields and leave them alone.
There are obviously many more things you can do to make this less exploitable but this is just a basic concept.
Although we all should know basic maths, the math puzzle could cause some confusion. In your example I'm sure some people would answer with "8" instead of "1".
Would a simple string of text with random characters highlighted in bold or italics be suitable? The user just needs to enter the bold/italic letters as the CAPTCHA.
E.g. ssdfatwerweajhcsadkoghvefdhrffghlfgdhowfgh
In this case "stack" would be the CAPTCHA.
There are obviously numerous variations on this idea.
Edit: Example variations to address some of the potential problems identified with this idea:
using randomly coloured letters instead of bold/italic.
using every second red letter for the CAPTCHA (reduces the possibility of bots identifying differently formatted letters to guess the CAPTCHA)
Although this similar discussion was started:
We are trying this solution on one of our frequently data mined applications:
A Better CAPTCHA Control (Look Ma - NO IMAGE!)
You can see it in action on our Building Inspections Search.
You can view Source and see that the CAPTCHA is just HTML.
I know that no one will read this, but what about the dog or cat CAPTCHA?
You need to say which one is a cat or a dog, machines can't do this..
http://research.microsoft.com/asirra/
Is a cool one..
I just use simple questions that anyone can answer:
What color is the sky?
What color is an orange?
What color is grass?
It makes it so that someone has to custom program a bot to your site, which probably isn't worth the effort. If they do, you just change the questions.
I personally do not like CAPTCHA it harms usability and does not solve the security issue of making valid users invalid.
I prefer methods of bot detection that you can do server side. Since you have valid users (thanks to OpenID) you can block those who do not "behave", you just need to identify the patterns of a bot and match it to patterns of a typical user and calculate the difference.
Davies, N., Mehdi, Q., Gough, N. : Creating and Visualising an Intelligent NPC using Game Engines and AI Tools http://www.comp.glam.ac.uk/ASMTA2005/Proc/pdf/game-06.pdf
Golle, P., Ducheneaut, N. : Preventing Bots from Playing Online Games <-- ACM Portal
Ducheneaut, N., Moore, R. : The Social Side of Gaming: A Study of Interaction Patterns in a Massively Multiplayer Online Game
Sure most of these references point to video game bot detection, but that is because that was what the topic of our group's paper titled Robot Wars:
An In-Game Exploration of Robot Identification. It was not published or anything, just something for a school project. I can email if you are interested. The fact is though that even if it is based on video game bot detection, you can generalize it to the web because there is a user attached to patterns of usage.
I do agree with MusiGenesis 's method of this approach because it is what I use on my website and it does work decently well. The invisible CAPTCHA process is a decent way of blocking most scripts, but that still does not prevent a script writer from reverse engineering your method and "faking" the values you are looking for in javascript.
I will say the best method is to 1) establish a user so that you can block when they are bad, 2) identify an algorithm that detects typical patterns vs. non-typical patterns of website usage and 3) block that user accordingly.
I have some ideas about that I like to share with you...
First Idea to avoid OCR
A captcha that have some hidden part from the user, but the full image is the two code together, so OCR programs and captcha farms reads the image that include the visible and the hidden part, try to decode both of them and fail to submit... - I have all ready fix that one and work online.
http://www.planethost.gr/IdeaWithHiddenPart.gif
Second Idea to make it more easy
A page with many words that the human must select the right one. I have also create this one, is simple. The words are clicable images, and the user must click on the right one.
http://www.planethost.gr/ManyWords.gif
Third Idea with out images
The same as previous, but with divs and texts or small icons. User must click only on correct one div/letter/image, what ever.
http://www.planethost.gr/ArrayFromDivs.gif
Final Idea - I call it CicleCaptcha
And one more my CicleCaptcha, the user must locate a point on an image. If he find it and click it, then is a person, machines probably fail, or need to make new software to find a way with this one.
http://www.planethost.gr/CicleCaptcha.gif
Any critics are welcome.
Best captcha ever! Maybe you need something like this for sign-up to keep the riff-raff out.
Recently, I started adding a tag with the name and id set to "message". I set it to hidden with CSS (display:none). Spam bots see it, fill it in and submit the form. Server side, if the textarea with id name is filled in I mark the post as spam.
Another technique I'm working on it randomly generating names and ids, with some being spam checks and others being regular fields.
This works very well for me, and I've yet to receive any successful spam. However, I get far fewer visitors to my sites :)
Very simple arithmetic is good. Blind people will be able to answer. (But as Jarod said, beware of operator precedence.) I gather someone could write a parser, but it makes the spamming more costly.
Sufficiently simple, and it will be not difficult to code around it. I see two threats here:
random spambots and the human spambots that might back them up; and
bots created to game Stack Overflow
With simple arithmetics, you might beat off threat #1, but not threat #2.
I've had amazingly good results with a simple "Leave this field blank:" field. Bots seem to fill in everything, particularly if you name the field something like "URL". Combined with strict referrer checking, I've not had a bot get past it yet.
Please don't forget about accessibility here. Captchas are notoriously unusable for many people using screen readers. Simple math problems, or very trivial trivia (I liked the "what color is the sky" question) are much more friendly to vision-impaired users.
Simple text sounds great. Bribe the community to do the work! If you believe, as I do, that SO rep points measure a user's commitment to helping the site succeed, it is completely reasonable to offer reputation points to help protect the site from spammers.
Offer +10 reputation for each contribution of a simple question and a set of correct answers. The question should suitably far away (edit distance) from all existing questions, and the reputation (and the question) should gradually disappear if people can't answer it. Let's say if the failure rate on correct answers is more than 20%, then the submitter loses one reputation point per incorrect answer, up to a maximum of 15. So if you submit a bad question, you get +10 now but eventually you will net -5. Or maybe it makes sense to ask a sample of users to vote on whether the captcha questionis a good one.
Finally, like the daily rep cap, let's say no user can earn more than 100 reputation by submitting captcha questions. This is a reasonable restriction on the weight given to such contributions, and it also may help prevent spammers from seeding questions into the system. For example, you could choose questions not with equal probability but with a probability proportional to the submitter's reputation. Jon Skeet, please don't submit any questions :-)
Make an AJAX query for a cryptographic nonce to the server. The server sends back a JSON response containing the nonce, and also sets a cookie containing the nonce value. Calculate the SHA1 hash of the nonce in JavaScript, copy the value into a hidden field. When the user POSTs the form, they now send the cookie back with the nonce value. Calculate the SHA1 hash of the nonce from the cookie, compare to the value in the hidden field, and verify that you generated that nonce in the last 15 minutes (memcached is good for this). If all those checks pass, post the comment.
This technique requires that the spammer sits down and figures out what's going on, and once they do, they still have to fire off multiple requests and maintain cookie state to get a comment through. Plus they only ever see the Set-Cookie header if they parse and execute the JavaScript in the first place and make the AJAX request. This is far, far more work than most spammers are willing to go through, especially since the work only applies to a single site. The biggest downside is that anyone with JavaScript off or cookies disabled gets marked as potential spam. Which means that moderation queues are still a good idea.
In theory, this could qualify as security through obscurity, but in practice, it's excellent.
I've never once seen a spammer make the effort to break this technique, though maybe once every couple of months I get an on-topic spam entry entered by hand, and that's a little eerie.
1) Human solvers
All mentioned here solutions are circumvented by human solvers approach. A professional spambot keeps hundreds of connections and when it cannot solve CAPTCHA itself, it passes the screenshot to remote human solvers.
I frequently read that human solvers of CAPTCHAs break the laws. Well, this is written by those who do not know how this (spamming) industry works.
Human solvers do not directly interact with sites which CAPTCHAs they solve. They even do not know from which sites CAPTCHAs were taken and sent them. I am aware about dozens (if not hundreds) companies or/and websites offering human solvers services but not a single one for direct interaction with boards being broken.
The latter do not infringe any law, so CAPTCHA solving is completely legal (and officialy registered) business companies. They do not have criminal intentions and might, for example, have been used for remote testing, investigations, concept proofing, prototypong, etc.
2) Context-based Spam
AI (Artificial Intelligent) bots determine contexts and maintain context sensitive dialogues at different times from different IP addresses (of different countries). Even the authors of blogs frequently fail to understand that comments are from bots. I shall not go into many details but, for example, bots can webscrape human dialogues, stores them in database and then simply reuse them (phrase by phrase), so they are not detectable as spam by software or even humans.
The most voted answer telling:
*"The theory being that:
A spam bot will not support JavaScript and will submit what it sees
If the bot does support JavaScript it will submit the form instantly
The commenter has at least read some of the page before posting"*
as well honeypot answer and most answers in this thread are just plain wrong.
I daresay they are victim-doomed approaches
Most spambots work through local and remote javascript-aware (patched and managed) browsers from different IPs (of different countries) and they are quite clever to circumvent honey traps and honey pots.
The different problem is that even blog owners cannot frequently detect that comments are from bot since they are really from human dialogs and comments harvested from other web boards (forums, blog comments, etc)
3) Conceptually New Approach
Sorry, I removed this part as precipitated one
Actually it could be an idea to have a programming related captcha set. For example:
There is the possibility of someone building a syntax checker to bypass this but it's a lot more work to bypass a captcha. You get the idea of having a related captcha though.
What if you used a combination of the captcha ideas you had (choose any of them - or select one of them randomly):
ASCII text captcha: //(_)//
math puzzles: what is 7 minus 3 times 2?
trivia questions: what tastes better, a toad or a popsicle?
with the addition of placing the exact same captcha in a css hidden section of the page - the honeypot idea. That way, you'd have one place where you'd expect the correct answer and another where the answer should be unchanged.
I have to admit that I have no experience fighting spambots and don't really know how sophisticated they are. That said, I don't see anything in the jQuery article that couldn't be accomplished purely on the server.
To rephrase the summary from the jQuery article:
When generating the contact form on the server ...
Grab the current time.
Combine that timestamp, plus a secret word, and generate a 32 character 'hash' and store it as a cookie on the visitor's browser.
Store the hash or 'token' timestamp in a hidden form tag.
When the form is posted back, the value of the timestamp will be compared to the 32 character 'token' stored in the cookie.
If the information doesn't match, or is missing, or if the timestamp is too old, stop execution of the request ...
Another option, if you want to use the traditional image CAPTCHA without the overhead of generating them on every request is to pre-generate them offline. Then you just need to randomly choose one to display with each form.