Feeds

Cross-site hacks and the art of self defence

The new browser wars

Using blade systems to cut costs and sharpen efficiencies

And what if you're at work or connected to the virtual private network? Your browser can go after the corporate portal. Do you have single sign-on? That means you're logged into every web application on your intranet, and your renegade browser can go after any of them.

Using CSRF, an attacker can attack all of these targets and can do just about anything you can do through your browser. All these attacks can be done remotely and basically anonymously.

Separate browsers

OK, so what can you do to protect yourself? First, don't stay logged into websites. You have to actually hit the log-out button, not just close the browser. Next, stop CSRF from getting to your critical websites by using a separate browser to access them. Companies are increasingly using separate browsers for accessing intranet applications and the internet - more should follow suit.

If your web application is attacked by a CSRF, all you'll see is normal transactions being performed by authenticated and authorised users. There won't be any way to tell that the user didn't actually execute the transaction. Probably the only way you'll find out that you have a CSRF problem is when users start complaining about phantom transactions on their account. The attacker can cover their tracks easily by removing the attack once it has worked.

Taken alone, CSRF attacks are simple and powerful. However, most attackers use CSRF and cross-site scripting (XSS) in conjunction. Together, these two techniques allow attackers to invade a victim's browser and execute malicious programs using the credentials of site the user is logged into.

This combination is devastating, and I'm frankly surprised that a cross-application CSRF-XSS worm hasn't already been developed.

The best solution to CSRF is to require a random token in each business function in your application. You can generate the random token when the user logs in and store it in their session. When you generate links and forms, simply add it to the URL or put it in a hidden form field. For example:

 

http://www.example.com?token=8FD41A&data=1

Requests that show up without the right token are forged and you can reject them. If you want to add protection without modifying code, the OWASP CSRFGuard is a filter that sits in front of your application and adds token support.

Whatever steps you take to protect yourself - whether it's the physical act of using different browsers or taking a token-based approach with the OWASP filter, make sure you do something - and soon. It will be difficult to roll out protection against forged requests once an attack has started.

Jeff Williams is the founder and CEO of Aspect Security and the volunteer chair of the Open Web Application Security Project. His latest project is the Enterprise Security API, a free and open set of foundational security building blocks for developers.

Boost IT visibility and business value

More from The Register

next story
Secure microkernel that uses maths to be 'bug free' goes open source
Hacker-repelling, drone-protecting code will soon be yours to tweak as you see fit
How long is too long to wait for a security fix?
Synology finally patches OpenSSL bugs in Trevor's NAS
Roll out the welcome mat to hackers and crackers
Security chap pens guide to bug bounty programs that won't fail like Yahoo!'s
Israel's Iron Dome missile tech stolen by Chinese hackers
Corporate raiders Comment Crew fingered for attacks
HIDDEN packet sniffer spy tech in MILLIONS of iPhones, iPads – expert
Don't panic though – Apple's backdoor is not wide open to all, guru tells us
Researcher sat on critical IE bugs for THREE YEARS
VUPEN waited for Pwn2Own cash while IE's sandbox leaked
Four fake Google haxbots hit YOUR WEBSITE every day
Goog the perfect ruse to slip into SEO orfice
prev story

Whitepapers

Implementing global e-invoicing with guaranteed legal certainty
Explaining the role local tax compliance plays in successful supply chain management and e-business and how leading global brands are addressing this.
Consolidation: The Foundation for IT Business Transformation
In this whitepaper learn how effective consolidation of IT and business resources can enable multiple, meaningful business benefits.
Application security programs and practises
Follow a few strategies and your organization can gain the full benefits of open source and the cloud without compromising the security of your applications.
How modern custom applications can spur business growth
Learn how to create, deploy and manage custom applications without consuming or expanding the need for scarce, expensive IT resources.
Securing Web Applications Made Simple and Scalable
Learn how automated security testing can provide a simple and scalable way to protect your web applications.