I'm developing a feature for a client in which users voluntarily take an important test online. The test is difficult and the users will be highly motivated to do well (think SATs or GRE, etc)... so there's also a high incentive to cheat. Apparently there are 3rd party services in which a human virtually monitors the test taker via a webcam, but they're really expensive and we don't quite have the budget. We still need to make it as hard as possible for a user to game the system. Some of the things we suspect they might try are:
Getting someone else to take the test for them (a pinch hitter).
Taking the test multiple times with different profiles to practice
and gain an unfair advantage.
Taking the test alongside friends or while in contact with a friends
to tell them the answers.
The question order will change, as well as the order of the answers. The test will be timed, and an "open book" format, so we're not really worried about the user looking things up online, but we can't have them sharing their screen and having others assist them. So the main concern at this point is ensuring that the user is, in fact, who they say they are (and not someone else).
Here are a few of the security measures we're considering:
Requiring the user's device to have a webcam, which we'll activate and either record/photograph the user during the test (with the user's consent of course).
Asking users to verify an arbitrary bank deposit amount (presumably via PayPal). There's nothing to stop them from opening up multiple bank accounts, but at least it's a big hassle.
Really scary terms of use that threaten legal action if the user is caught cheating.
QUESTION: Are there any other measure we can/should take to make sure our test is secure and the results are reliable?
CLARIFICATION: We realize that with enough resources and determination, any security system can eventually be beaten. The goal of this question is not to find a magically unbeatable solution, but to find ways to raise the stakes enough so that it won't be worth it for most users to cheat. In this spirit, I'd much prefer answers that focus on what can be done as opposed to what can't.
As you know there are many ways of cheating. Your goal is limit the possibility of cheating as much as possible. Cheating in online courses has been a hot topic.
A pinch hitter:
This type of attack can be conducted a number of ways. Even if you have a cam looking at the person, the video that the test taker is seeing could be mirrored on another screen. A pinch hitter could see the question and just read him the answers or otherwise feed answers the test taker in a covert channel.
Possible counters to this attack is to also enable the mic to see if they are talking to anyone. You can also record the screen while they take the test. This could prevent them from opening a chat window or viewing other unauthorized content. (Kind of like the Elance tracker)
user verification:
In order to register the person should attach a scanned copy of their photo-id. This way you are linking a photo of the person to a unique identifier, such as a drivers license number. Before the person starts taking the test, ask the user to look directly at the camera and make sure you get a good image of them that can be verified against their photo id.
A simple attack against this system is to use photoshop to modify the id. To make this attack more difficult you could verify their name against a credit/debit card transaction. The names should match on both cards.
An evercookie could be used to track machines to see if the same computer is being used. This could happen though legitimate reasons, but it could also be used to flag tests for further review. A variant on the evercookie is to drop a file with a random value or set a registry key with a random value to "mark" that machine.
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.
I would like to know what we can mean by saying a optimized security system(physical or logical security system).
Does it mean something like a system which can monitor performance of services, SQL, DB maintenance, logs etc.
Thanks
Optimized is a general term, you will have to get specific in terms of defining what you need to consider it optimized to an "acceptable" level. Plus there are different kinds of "optimization", such as for speed, memory usage, maintainability, etc.
Are you trying to figure out some criteria so that you can market your product as "optimized" and be able to explain it if someone asks what you mean?
If so, you need to figure out what your customers (or potential customers) actually care about. If they care about video resolution and disk space usage (how much the system can store before having to archive elsewhere), then you need to make your application smart (optimized! :) in those areas.
THEN, you could be more specific in your marketing and say, "optimized to use XYZ resolution and store up to 2 weeks of video on a standard hardware setup!" - which would actually mean something tangible to your customers, and show them that you care about what they care about.
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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.