Feeds

Cross-site hacks and the art of self defence

The new browser wars

SANS - Survey on application security programs

Hackers can force your browser to send requests to any site they want. It's not even hard - all they have to do is get you to view an email or a web page.

Unless the site is specifically protected against this - and almost none are - then attackers can make your browser do anything you can do, and they can use your credentials and your access privileges. They can do things like set preferences, create payees and change passwords.

Generally, browsers stop cross-site communication by following the "same-origin policy". This rule is pretty simple: if your site has a different origin - protocol, domain, and port don't all match - you aren't allowed to access information from or send requests to the other site. Without this simple rule, there would be no security on the internet. Every website could access data from every other one - you'd need a separate web browser for every website.

Unfortunately, the same-origin policy is nowhere near airtight. Attackers don't even need an exploit to bypass it. They can simply embed an IMG, SCRIPT, IFRAME, or FORM tag that references the targeted website in an HTML page. When the victim's browser renders this tag, it generates a request and sends it to the targeted website - right around the same-origin policy. This is a feature of all browsers - it's used by many applications to grab images from other sites and to post from data to services.

Attackers can use this loophole to forge requests that appear to be coming from a legitimate user. These are called cross-site request forgeries, or CSRF, for short. Take a look at the old CSRF attack on Netflix, below.

 

<img src=http://www.netflix.com/AddToQueue?movieid=70011204 width="1" height="1" border="0">
Attackers can submit forms on your behalf as well.
<body onload="document.forms[0].submit()">
<form method="POST" action="https://bank.com/transfer.do">
       <input type="hidden" name="account" value="123456789"/>
       <input type="hidden" name="amount" value="2500"/>
</form>

The attacker can post this image tag anywhere - a blog, a wiki, a website, even an email message. Anyone who accidentally browses a page containing the attack while logged into Netflix will have a movie silently added to their queue.

More complex attacks involve a sending series of requests and delays, allowing the attacker to execute a series of actions in a row. In a strange way, a CSRF attack is a sort of program that executes web instructions on behalf of the attacker.

Imagine your browser suddenly turned evil and started trying to mess up your life. What could it do? It might raid the email account you're currently logged into. Maybe it would go after any bank accounts and healthcare sites you're using. Did you click "remember my login" on any websites? Guess what, your renegade browser is logged in and can take over those accounts.

Combat fraud and increase customer satisfaction

Next page: Separate browsers

More from The Register

next story
Parent gabfest Mumsnet hit by SSL bug: My heart bleeds, grins hacker
Natter-board tells middle-class Britain to purée its passwords
Obama allows NSA to exploit 0-days: report
If the spooks say they need it, they get it
Web data BLEEDOUT: Users to feel the pain as Heartbleed bug revealed
Vendors and ISPs have work to do updating firmware - if it's possible to fix this
Samsung Galaxy S5 fingerprint scanner hacked in just 4 DAYS
Sammy's newbie cooked slower than iPhone, also costs more to build
Mounties always get their man: Heartbleed 'hacker', 19, CUFFED
Canadian teen accused of raiding tax computers using OpenSSL bug
Snowden-inspired crypto-email service Lavaboom launches
German service pays tribute to Lavabit
One year on: diplomatic fail as Chinese APT gangs get back to work
Mandiant says past 12 months shows Beijing won't call off its hackers
prev story

Whitepapers

Designing a defence for mobile apps
In this whitepaper learn the various considerations for defending mobile applications; from the mobile application architecture itself to the myriad testing technologies needed to properly assess mobile applications risk.
3 Big data security analytics techniques
Applying these Big Data security analytics techniques can help you make your business safer by detecting attacks early, before significant damage is done.
Five 3D headsets to be won!
We were so impressed by the Durovis Dive headset we’ve asked the company to give some away to Reg readers.
The benefits of software based PBX
Why you should break free from your proprietary PBX and how to leverage your existing server hardware.
Securing web applications made simple and scalable
In this whitepaper learn how automated security testing can provide a simple and scalable way to protect your web applications.