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There are lots of ways to create a login form for web apps and most of them are flawed one way or the other:
Passwords are transmitted/saved as clear text
The login dialogs are subject to XSS attacks or SQL injection
Is there an example or tutorial how to create a secure login form?
I agree with Carlos about lack of "perfect" secure system, not only for login, but for any other component. The only thing to do is to minimize risks by following best practices, but always keeping in mind that total safety doesn't exist, so your question is quite difficult to answer, although there are some good examples out there nothing is perfect, security is a very fast evolving topic.
For me the main things to solve are:
-Data transmission: The user is always going to type a password and this has to be sent to your system before it was processed, so there is a high risk of being intercepted if you are using an open channel. To solve this you MUST use transport the data over an encrypted channel (SSL), no other way unless you drop the common password (for example using one-time use tokens, or delegating the authentication to a third party, like Facebook connect or openId). See "How to Make a Secure Login Form with SSL"
-Input Sanitation: To avoid XSS and SQL Injection consider any input that comes from a client as a potentially risk point, therefore you have to perform validation against anything that comes form outside --> doc. Another good practice is never use the inputs directly on queries, use as bind variables in prepared statements or stored procedures.
-Password Storage: Password should always be stored encrypted with a one way hash algorithm, so even in the case of someone accessing your DB, there is no way to recover the original passwords. Also use techniques as Salting, Hashing multiple times, etc... Also be careful to choose an algorithm that is not weak or outdated (like MD5), which can be broken by brute force easily with the increasing CPU power.
-Infrastructure: Have your machines, OS, frameworks, libraries always updated to avoid bugs and 0 day attack. Any system today is enormously complex, and the system is as secure as it weakest component.
-Other Things to Consider: Review your security policy regularly to see if needs to update anything, implement password policies (expiration, reuse, etc...), log access, use monitoring tools for your systems, etc etc etc
And after all that, you can still be sure that if someone has enough time and resources, your system will fall.
Your question, can't be that agnostic, and must be divided in your two main concerns:
Transmitting passwords in the clear.
Xss, Sql injection.
No system will be declared secured per se, but you can try your best to minimize the risks by using proven concepts.
So let's say you have the chance to design your own "secure system", what do you need?
At minimum you will need a basic set of tools:
Client side data encripting: (Javascript here, i think you will find lots of info of how to send your data in data 64 or something like that, remember you are searching for one way or two way encription)
DB Encription: (One way-two way encription, but never save passwords in the clear)
SQl injection: (mysql_real_escape_string() comes to mind).
Every language has some sort of protection built in, it is when building large projects that sometimes we may forget to sanitize some querys
I repeat no system will ever be declared secure, however you can add some other security measures as in:
access_tokens = timed-strings that allow to validate user login.
captcha_after_few_intents = you should add this definitely.
block_account_after_few_trys = pain in the * for users, but definitely worth it.
login_token = store a token unique for that user, and use it in all GET/POST transactions
SSL
From Bank Security:
Automatic gsm devices that generates RANDS and access_tokens valid only for a short time.
mouse keyboard: evitates keyloggers
random_access_question:
check_random_account_country_change = let's say user is from albany and next day he logs in from south america, that should maybe raise a flag to your system.
I'm sure you will find plenty of advice somewhere, but remember you at end will end talking html, and some js, your main defense is on the server side, so be good, or be good at it.
Related
I'm on my last steps to open my website, but the only thing that drove me crazy is the php user management. I found a lot of resources about building these systems and I believe that I can write them in my own way. The thing is that when it comes to security I get so freaking out what to go with. For example, when it comes to sending sensitive information over SSL, some people suggest to make sure that the info is encrypted in the registration form so that attacker can't hack it. And some other suggest to make sure that the debugging messages don't show when an error happen so that the attacker can't retrace the links .etc.
now as I read from here and there that md5 is not safe anymore so I'm wondering how would hash new user password and etc... I found a link to some programmers who already offer some user management, but not sure if they are good enough since I'm concerned about security as a priority CodeCanyon
so now what are the security measures that I have to be focusing on?
are there any resources related to that?
Thanks,
You don't have to (you shouldn't) choose between the different things people tell you to implement. Good security is always layered, meaning that you implement as many protections as you can. This approach has multiple purposes. Each layer can prevent different attacks. Each layer can prevent attackers with different experience. Each layer can increase the time needed for an attacker.
Here are some tipps useful for authentication systems.
Don't show debugging outputs
Don't use MD5 hashes. SHA2 or even better, bcrypt are much better
Use salts when storing passwords
Use nonces on your forms (one time tokens)
Always require SSL encryption between server and client
When accessing your database on the server, make sure that information leakage or its client-side manipulation not possible (eg.
avoid injection attacks, with database drivers use prepared
statements, etc.)
Make sure all failed logins (no matter what the reason) take the same amount of time to prevent timing attacks
When a logged-in user starts a risky operation (changing pwd, payment etc.), re-authgenticate him
Never store passwords cleartext, not ever, not anywhere
Require a minimum complexity for the password
!!! Secure your php sessions (another large topic, worth its own discussion) -
As you can see, there a lot you can do (and more people will probably tell you even more stuff), what you really should do depends on the risks you are willing to accept. But never rely on a single security measure, always have a layered approach.
Answering your direct question: It has been proven that MD5 does have collisions and there are rainbow tables floating around (see Wikipedia). PHP does have quite some hash functions available all having different advantages and disadvantages. Please also see the comment section on php.net.
Concerning general web application security I'd recommend you take a look at the OWASP project that is about making web applications more secure. A good start would be to take a look at the Top Ten security vunerabilities ("Top Ten" in the blue box).
use sha1 for storing password , prevent sql injection and xss script as input field.
session hijacking , fixation prevention.
At first you should send your data via SSL (TSL) to the server, this will encrypt. Also you should use a CSRF protection for any form you send to the server.
When you have implemented your functions and they work you should try to hack your site by yourself. Try to inject SQL, JS through the forms, try to manipulate the date after the form was send, you can also try to produce erros that will be written to you PHP error log even that could be executed if your server settings are weak. (http://en.wikipedia.org/wiki/Hardening_(computing))
When you store the password in your database use an seeded hash function, if anyone is able to hack your database and get the hashs he will not be able to encrypt them without the seed.
Your will find many information about all the techniques via google.
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From what I understand, you have to enter in all of your usernames and passwords into Mint, so I assume they are actually logging into your bank account and scraping the resulting screen to put this data into a form that Mint and others use.
How do they actually simulate the keypresses and mouse clicks? I assume banks don't like it when they do this - how do their scrapers avoid detection?
I'm pretty sure they don't simulate clicks, etc. In the end, any data that ends up on a user's page is transmitted in a response to a request. If you can figure out how to construct a valid request and then how to parse the response, you'll have the data you want.
As far as I could gather after using Yodlee for quite a while, they deal with sites in two major ways: the sites they have official agreements to work with and the sites they don't have official agreements with. For the first category of sites they, most often, have agreed upon APIs for getting the data. For the sites in the second category they reverse-engineer layer 7 communication protocols and data structures (a.k.a. screen/html scraping).
The way I understand it, Yodlee uses the OFX specification to access banks' financial information.
http://www.ofx.net/
For the banks that don't implement OFX, they use custom screen scrapers, which must constantly be updated when banks change the information that's displayed on their site.
I don't know Yodlee so i simply assume it's like "sofortüberweisung.de" where you give a 3rd party your bank login data (and depending on what you do even a valid TAN) and thus trust them not to abuse it and additionally break your bank's security regulations ("NEVER GIVE YOUR YOUR PIN/TAN").
They most likely simulate what a browser would do. As web-based banking interfaces are usually just HTML/JavaScript everyone can look at the client-side code and do whatever it does with a custom program. Since those actions are not done in a malicious way, actions which require e.g. a TAN or a CAPTCHA to be solved can be simply forwarded to the legit user who will then enter the necessary TAN or solve the CAPTCHA.
Nonetheless to say, it is really bad to use services like that. While they most likely won't do anything bad you cannot know it for sure. And your bank is damn right if they don't refund you anything if you ever get scammed by such a service.
Another solution which would be perfectly safe (as long as you are not concerned about a 3rd party knowing about your financial status etc.) would be the yodlee company making contracts with major banks allowing them to access your data after you've authorized it through some way (you can already do that on pages like Twitter - I'd never do that for bankign though but technically it wouldn't be hard to realize something like that). That would be clean and secure as it would not involve "screen-scraping" or customers entering their banking login data anywhere but on their bank's website. But I believe no bank does something like that and in my opinion that's good as there are way too many people out there who are far too trustworthy and we all know how many information they give out on Facebook & Co. Now imagine a facebook<->bank integration... M.Zuck.'s wet dreams which hopefully never become true... And even if it's not Facebook.. There'll always be companies who want people's personal data and enough people giving them out; especially if it's easy and looks secure ("I have to confirm it on MY BANK's page. so it MUST be safe - it's supported by MY BANK").
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I am an IT student and I am now in the 3rd year in university. Until now we've been studing a lot of subjects related to computers in general (programming, algorithms, computer architecture, maths, etc).
I am very sure that nobody can learn every thing about security but sure there is a "minimum" knowledge every programmer or IT student should know about it and my question is what is this minimum knowledge?
Can you suggest some e-books or courses or anything can help to start with this road?
Principles to keep in mind if you want your applications to be secure:
Never trust any input!
Validate input from all untrusted sources - use whitelists not blacklists
Plan for security from the start - it's not something you can bolt on at the end
Keep it simple - complexity increases the likelihood of security holes
Keep your attack surface to a minimum
Make sure you fail securely
Use defence in depth
Adhere to the principle of least privilege
Use threat modelling
Compartmentalize - so your system is not all or nothing
Hiding secrets is hard - and secrets hidden in code won't stay secret for long
Don't write your own crypto
Using crypto doesn't mean you're secure (attackers will look for a weaker link)
Be aware of buffer overflows and how to protect against them
There are some excellent books and articles online about making your applications secure:
Writing Secure Code 2nd Edition - I think every programmer should read this
Building Secure Software: How to Avoid Security Problems the Right Way
Secure Programming Cookbook
Exploiting Software
Security Engineering - an excellent read
Secure Programming for Linux and Unix HOWTO
Train your developers on application security best pratices
Codebashing (paid)
Security Innovation(paid)
Security Compass (paid)
OWASP WebGoat (free)
Rule #1 of security for programmers: Don't roll your own
Unless you are yourself a security expert and/or cryptographer, always use a well-designed, well-tested, and mature security platform, framework, or library to do the work for you. These things have spent years being thought out, patched, updated, and examined by experts and hackers alike. You want to gain those advantages, not dismiss them by trying to reinvent the wheel.
Now, that's not to say you don't need to learn anything about security. You certainly need to know enough to understand what you're doing and make sure you're using the tools correctly. However, if you ever find yourself about to start writing your own cryptography algorithm, authentication system, input sanitizer, etc, stop, take a step back, and remember rule #1.
Every programmer should know how to write exploit code.
Without knowing how systems are exploited you are accidentally stopping vulnerabilities. Knowing how to patch code is absolutely meaningless unless you know how to test your patches. Security isn't just a bunch of thought experiments, you must be scientific and test your experiments.
Security is a process, not a product.
Many seem to forget about this obvious matter of fact.
I suggest reviewing CWE/SANS TOP 25 Most Dangerous Programming Errors. It was updated for 2010 with the promise of regular updates in the future. The 2009 revision is available as well.
From http://cwe.mitre.org/top25/index.html
The 2010 CWE/SANS Top 25 Most Dangerous Programming Errors is a list of the most widespread and critical programming errors that can lead to serious software vulnerabilities. They are often easy to find, and easy to exploit. They are dangerous because they will frequently allow attackers to completely take over the software, steal data, or prevent the software from working at all.
The Top 25 list is a tool for education and awareness to help programmers to prevent the kinds of vulnerabilities that plague the software industry, by identifying and avoiding all-too-common mistakes that occur before software is even shipped. Software customers can use the same list to help them to ask for more secure software. Researchers in software security can use the Top 25 to focus on a narrow but important subset of all known security weaknesses. Finally, software managers and CIOs can use the Top 25 list as a measuring stick of progress in their efforts to secure their software.
A good starter course might be the MIT course in Computer Networks and Security. One thing that I would suggest is to not forget about privacy. Privacy, in some senses, is really foundational to security and isn't often covered in technical courses on security. You might find some material on privacy in this course on Ethics and the Law as it relates to the internet.
The Web Security team at Mozilla put together a great guide, which we abide by in the development of our sites and services.
The importance of secure defaults in frameworks and APIs:
Lots of early web frameworks didn't escape html by default in templates and had XSS problems because of this
Lots of early web frameworks made it easier to concatenate SQL than to create parameterized queries leading to lots of SQL injection bugs.
Some versions of Erlang (R13B, maybe others) don't verify ssl peer certificates by default and there are probably lots of erlang code that is susceptible to SSL MITM attacks
Java's XSLT transformer by default allows execution of arbitrary java code. There has been many serious security bugs created by this.
Java's XML parsing APIs by default allow the parsed document to read arbitrary files on the filesystem. More fun :)
You should know about the three A's. Authentication, Authorization, Audit. Classical mistake is to authenticate a user, while not checking if user is authorized to perform some action, so a user may look at other users private photos, the mistake Diaspora did. Many, many more people forget about Audit, you need, in a secure system, to be able to tell who did what and when.
Remember that you (the programmer) has to secure all parts, but the attacker only has to succeed in finding one kink in your armour.
Security is an example of "unknown unknowns". Sometimes you won't know what the possible security flaws are (until afterwards).
The difference between a bug and a security hole depends on the intelligence of the attacker.
I would add the following:
How digital signatures and digital certificates work
What's sandboxing
Understand how different attack vectors work:
Buffer overflows/underflows/etc on native code
Social engineerring
DNS spoofing
Man-in-the middle
CSRF/XSS et al
SQL injection
Crypto attacks (ex: exploiting weak crypto algorithms such as DES)
Program/Framework errors (ex: github's latest security flaw)
You can easily google for all of this. This will give you a good foundation.
If you want to see web app vulnerabilities, there's a project called google gruyere that shows you how to exploit a working web app.
when you are building any enterprise or any of your own software,you should just think like a hacker.as we know hackers are also not expert in all the things,but when they find any vulnerability they start digging into it by gathering information about all the things and finally attack on our software.so for preventing such attacks we should follow some well known rules like:
always try to break your codes(use cheatsheets & google the things for more informations).
be updated for security flaws in your programming field.
and as mentioned above never trust in any type of user or automated inputs.
use opensource applications(their most security flaws are known and solved).
you can find more security resource on the following links:
owasp security
CERT Security
SANS Security
netcraft
SecuritySpace
openwall
PHP Sec
thehackernews(keep updating yourself)
for more information google about your application vendor security flows.
Why is is important.
It is all about trade-offs.
Cryptography is largely a distraction from security.
For general information on security, I highly recommend reading Bruce Schneier. He's got a website, his crypto-gram newsletter, several books, and has done lots of interviews.
I would also get familiar with social engineering (and Kevin Mitnick).
For a good (and pretty entertaining) book on how security plays out in the real world, I would recommend the excellent (although a bit dated) 'The Cuckoo's Egg' by Cliff Stoll.
Also be sure to check out the OWASP Top 10 List for a categorization of all the main attack vectors/vulnerabilities.
These things are fascinating to read about. Learning to think like an attacker will train you of what to think about as you're writing your own code.
Salt and hash your users' passwords. Never save them in plaintext in your database.
Just wanted to share this for web developers:
security-guide-for-developershttps://github.com/FallibleInc/security-guide-for-developers
this question can be associated to a subjective question, but this is not a really one.
When you develop a website, there is several points you must know: XSS attacks, SQL injection, etc.
It can be very very difficult (and take a long time to code) to secure all potential attacks.
I always try to secure my application but I don't know when to stop.
Let's take the same example: a social networking like Facebook. (Because a bank website must secure all its datas.)
I see some approaches:
Do not secure XSS, SQL injection... This can be really done when you trust your user: back end for a private enterprise. But do you secure this type of application?
Secure attacks only when user try to access non owned datas: This is for me the best approach.
Secure all, all, all: You secure all datas (owner or not): the user can't break its own datas and other user datas: this is very long to do and is it very useful?
Secure common attacks but don't secure very hard attacks (because it's too long to code comparing to the chance of being hacked).
Well, I don't know really what to do... For me, I try to do 1, 2, 4 but I don't know if it's the great choice.
Is there an acceptable risk to not secure all your datas? May I secure all datas but it takes me double time to code a thing? What's the enterprise approach between risk and "time is money"?
Thank you to share this because I think a lot of developers don't know what is the good limit.
EDIT: I see a lot of replies talking about XSS and SQL injection, but this is not the only things to take care about.
Let's take a forum. A thread can be write in a forum where we are moderator. So when you send data to client view, you add or remove the "add" button for this forum. But when a user tries to save a thread in server side, you must check that user has the right to dot it (you can't trust on client view security).
This is a very simple example, but in some of my apps, I've got a hierarchy of rights which can be very very difficult to check (need a lot of SQL queries...) but in other hand, it's really hard to find the hack (datas are pseudo encrypted in client view, there is a lot of datas to modify to make the hack runs, and the hacker needs a good understanding of my app rules to do a hack): in this case, may I check only surface security holes (really easy hack) or may I check very hard security holes (but it will decrease my performances for all users, and takes me a long time to develop).
The second question is: Can we "trust" (to not develop a hard and long code which decreases performance) on client view for very hard hack?
Here is another post talking of this sort of hack: (hibernate and collection checking) Security question: how to secure Hibernate collections coming back from client to server?
I think you should try and secure everything you can, the time spent doing this is nothing compared to the time needed to fix the mess done by someone exploiting a vulnerability you left somewhere.
Most things anyway are quite easy to fix:
sql injections have really nothing to do with sql, it's just string manipulation, so if you don't feel comfortable with that, just use prepared statements with bound parameters and forget about the problem
cross site exploit are easily negated by escaping (with htmlentities or so) every untrusted data before sending it out as output -- of course this should be coupled with extensive data filtering, but it's a good start
credentials theft: never store data which could provide a permanent access to protected areas -- instead save a hashed version of the username in the cookies and set a time limit to the sessions: this way an attacker who might happen to steal this data will have a limited access instead of permanent
never suppose that just because a user is logged in then he can be trusted -- apply security rules to everybody
treat everything you get from outside as potentially dangerous: even a trusted site you get data from might be compromised, and you don't want to fall down too -- even your own database could be compromised (especially if you're on a shared environment) so don't trust its data either
Of course there is more, like session hijacking attacks, but those are the first things you should look at.
EDIT regarding your edit:
I'm not sure I fully understand your examples, especially what you mean by "trust on client security". Of course all pages with restricted access must start with a check to see if the user has rights to see the content and optionally if he (or she) has the correct level of privilege: there can be some actions available to all users, and some others only available to a more restricted group (like moderators in a forum). All this controls have to be done on the server side, because you can never trust what the client sends you, being it data through GET, POST and even COOKIES. None of these are optional.
"Breaking data" is not something that should ever be possible, by the authorized user or anybody else. I'd file this under "validation and sanitation of user input", and it's something you must always do. If there's just the possibility of a user "breaking your data", it'll happen sooner or later, so you need to validate any and all input into your app. Escaping SQL queries goes into this category as well, which is both a security and data sanitation concern.
The general security in your app should be sound regardless. If you have a user management system, it should do its job properly. I.e. users that aren't supposed to access something should not be able to access it.
The other problem, straight up XSS attacks, has not much to do with "breaking data" but with unauthorized access to data. This is something that depends on the application, but if you're aware of how XSS attacks work and how you can avoid them, is there any reason not to?
In summary:
SQL injection, input validation and sanitation go hand in hand and are a must anyway
XSS attacks can be avoided by best-practices and a bit of consciousness, you shouldn't need to do much extra work for it
anything beyond that, like "pro-active" brute force attack filters or such things, that do cause additional work, depend on the application
Simply making it a habit to stick to best practices goes a long way in making a secure app, and why wouldn't you? :)
You need to see web apps as the server-client architecture they are. The client can ask a question, the server gives answers. The question is just a URL, sometimes with a bit of attached POST data.
Can I have /forum/view_thread/12345/ please?
Can I POST this $data to /forum/new_thread/ please?
Can I have /forum/admin/delete_all_users/ please?
Your security can't rely only on the client not asking the right question. Never.
The server always needs to evaluate the question and answer No when necessary.
All applications should have some degree of security. You generally don't ask for SSL on intranet websites, but you need to take care of SQL/XSS attacks.
All data your user enters into your application should be under your responsibility. You must make sure nobody unauthorized get access to it. Sometimes, a "not critical" information can pose a very security problem, because we're all lazy people.
Some time ago, a friend used to run a games website. Users create their profiles, forum , all that stuff. Then, some day, someone found a SQL injection open door somewhere. That attacker get all user and password information.
Not a big deal, huh? I mean, who cares about a player account into a website? But most users used same user/password to MSN, Counter Strike, etc. So become a big problem very fast.
Bottom line is: all applications should have some security concern. You should take a look into STRIDE to understand your attack vectors and take best action.
I personally prefer to secure everything at all times. It might be a paranoid approach, but when I see tons of websites throughout internet, that are vulnerable to SQL injection or even much simpler attacks, and they are not bothered to fix it until someone "hacks" them and steal their precious data, it makes me pretty much afraid. I don't really want to be the one responsible for leaked passwords or other user info.
Just ask someone with hacking experiences to check your application / website. It should give you a fair idea what's wrong and what should be updated.
You want to have strong API side ACL. Some days ago I saw a problem where a guy had secured every single UI, but the website was vulnerable through AJAX, just because his API (where he was sending requests) just trusted every single request to be checked. I could basically pull whole database through this bug.
I think it's helpful to distinguish between preventing code injection and plain data authorization.
In my opinion, all it takes is a few good coding habits to completely eliminate SQL injection. There is simply no excuse for it.
XSS injection is a little bit different - i think it can always be prevented, but it may not be trivial if your application features user generated content. By that I simply mean that it may not be as trivial to secure your app against XSS as it is compared to SQL injection. So I do not mean that it is ok to allow XSS - I still think there is no excuse for allowing it, it's just harder to prevent than SQL injection if your app revolves around user generated content.
So SQL injection and XSS are purely technical matters - the next level is authorization: how thoroughly should one shield of access to data that is no business of the current user. Here I think it really does depend on the application, and I can imagine that it makes sense to distinguish between: "user X may not see anything of user Y" vs "Not bothering user X with data of user Y would improve usability and make the application more convenient to use".
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Regarding Agile development, what are the best practices for testing security per release?
If it is a monthly release, are there shops doing pen-tests every month?
What's your application domain? It depends.
Since you used the word "Agile", I'm guessing it's a web app. I have a nice easy answer for you.
Go buy a copy of Burp Suite (it's the #1 Google result for "burp" --- a sure endorsement!); it'll cost you 99EU, or ~$180USD, or $98 Obama Dollars if you wait until November.
Burp works as a web proxy. You browse through your web app using Firefox or IE or whatever, and it collects all the hits you generate. These hits get fed to a feature called "Intruder", which is a web fuzzer. Intruder will figure out all the parameters you provide to each one of your query handlers. It will then try crazy values for each parameter, including SQL, filesystem, and HTML metacharacters. On a typical complex form post, this is going to generate about 1500 hits, which you'll look through to identify scary --- or, more importantly in an Agile context, new --- error responses.
Fuzzing every query handler in your web app at each release iteration is the #1 thing you can do to improve application security without instituting a formal "SDLC" and adding headcount. Beyond that, review your code for the major web app security hot spots:
Use only parameterized prepared SQL statements; don't ever simply concatenate strings and feed them to your database handle.
Filter all inputs to a white list of known good characters (alnum, basic punctuation), and, more importantly, output filter data from your query results to "neutralize" HTML metacharacters to HTML entities (quot, lt, gt, etc).
Use long random hard-to-guess identifiers anywhere you're currently using simple integer row IDs in query parameters, and make sure user X can't see user Y's data just by guessing those identifiers.
Test every query handler in your application to ensure that they function only when a valid, logged-on session cookie is presented.
Turn on the XSRF protection in your web stack, which will generate hidden form token parameters on all your rendered forms, to prevent attackers from creating malicious links that will submit forms for unsuspecting users.
Use bcrypt --- and nothing else --- to store hashed passwords.
I'm no expert on Agile development, but I would imagine that integrating some basic automated pen-test software into your build cycle would be a good start. I have seen several software packages out there that will do basic testing and are well suited for automation.
I'm not a security expert, but I think the most important fact you should be aware of, before testing security, is what you are trying to protect. Only if you know what you are trying to protect, you can do a proper analysis of your security measures and only then you can start testing those implemented measures.
Very abstract, I know. However, I think it should be the first step of every security audit.
Unit testing, Defense Programming and lots of logs
Unit testing
Make sure you unit test as early as possible (e.g. the password should be encrypted before sending, the SSL tunnel is working, etc). This would prevent your programmers from accidentally making the program insecure.
Defense Programming
I personally call this the Paranoid Programming but Wikipedia is never wrong (sarcasm). Basically, you add tests to your functions that checks all the inputs:
is the user's cookies valid?
is he still currently logged in?
are the function's parameters protected against SQL injection? (even though you know that the input are generated by your own functions, you will test anyway)
Logging
Log everything like crazy. Its easier to remove logs then to add them. A user have logged in? Log it. A user found a 404? Log it. The admin edited/deleted a post? Log it. Someone was able to access a restricted page? Log it.
Don't be surprised if your log file reaches 15+ Mb during your development phase. During beta, you can decide which logs to remove. If you want, you can add a flag to decide when a certain event is logged.