Feeds

Microsoft's IE 8 puts giant web hole on notice

Tell us if you've heard this one before?

Secure remote control for conventional and virtual desktops

Engineers in Microsoft's Internet Explorer group are devising a new means to stamp out one of the web's biggest security banes: attacks that steal email, bank account credentials and other sensitive information by injecting malicious code into trusted websites.

Some of the web's biggest names - including Google, Yahoo and MySpace - have fallen victim to so-called cross-site scripting (XSS) attacks. Tens of thousands of other sites, some belonging to banks and health care providers, have also been been shown to be vulnerable. For the past few years, Firefox users have had the useful - but by no means perfect - NoScript plugin to insulate them, but currently no such protection exists for IE, which remains far and away the most popular browser.

That all will change with IE 8. Last month, Microsoft announced a new XSS filter that will be folded into the new browser. Microsoft earlier this week provided new details about its plans.

Specifically, engineers will take pains to ensure the XSS filter doesn't "break the web" by choking on false positives or slowing down the browsing experience. Cryptic error messages or dialog boxes are out. And so are overly aggressive filters that block legitimate sites or open users up to new types of attacks.

"It is challenging to mitigate XSS in a way that balances the needs of compatibility, security, and performance," David Ross, a Microsoft Security Vulnerability Research & Defense blogger writes.

To prevent performance bottlenecks, the filter only acts on web pages that can result in the execution of scripts, so objects such as images that don't include scripts are ignored. The filter also gives a green light to code that's found to originate from the site the user is visiting. The filter can also be disabled for specific zones, based on an administrator's preferences.

When the filter encounters a script that is hosted on a site other than the one being visited, a heuristics engine is started that inspects the URL and POST data of the requested page and uses regular expressions to identify possible XSS vulnerabilities. The filter scours the URL for suspicious characters such as script tags. When suspicious characters are found, the filter kicks into action by inspecting the HTTP code and generating a signature.

Signatures are then compared against the HTTP response and scripts found to be malicious are neutered. Instead of running the code, IE displays a message that says the page has been modified to prevent an XSS attack.

Rival security researchers have wasted no time in criticizing the approach. Giorgio Maone, the creator of NoScript, said the the filter is likely to miss many attacks because of the requirement that it check the HTTP responses for actual reflection. Attacks that use pure JavaScript or that don't fully echo back to a browser may not be flagged, he says.

"If you deploy a security feature already knowing how to work-around it, I think it's more security theater than anything else," he told The Reg in an email.

Maybe. But the filter does have its proponents, among them Dave Aitel, CTO of Immunity Security. Because IE compares a web request to the page that's returned, the filter ought to be able to make informed decisions about whether an attack is taking place.

"That's more aggressive than anyone else is being other than Firefox," he says.

Microsoft's blog post is here. ®

Beginner's guide to SSL certificates

More from The Register

next story
You really need to do some tech support for Aunty Agnes
Free anti-virus software, expires, stops updating and p0wns the world
Regin: The super-spyware the security industry has been silent about
NSA fingered as likely source of complex malware family
You stupid BRICK! PCs running Avast AV can't handle Windows fixes
Fix issued, fingers pointed, forums in flames
Privacy bods offer GOV SPY VICTIMS a FREE SPYWARE SNIFFER
Looks for gov malware that evades most antivirus
Patch NOW! Microsoft slings emergency bug fix at Windows admins
Vulnerability promotes lusers to domain overlords ... oops
HACKERS can DELETE SURVEILLANCE DVRS remotely – report
Hikvision devices wide open to hacking, claim securobods
prev story

Whitepapers

Choosing cloud Backup services
Demystify how you can address your data protection needs in your small- to medium-sized business and select the best online backup service to meet your needs.
A strategic approach to identity relationship management
ForgeRock commissioned Forrester to evaluate companies’ IAM practices and requirements when it comes to customer-facing scenarios versus employee-facing ones.
Go beyond APM with real-time IT operations analytics
How IT operations teams can harness the wealth of wire data already flowing through their environment for real-time operational intelligence.
The total economic impact of Druva inSync
Examining the ROI enterprises may realize by implementing inSync, as they look to improve backup and recovery of endpoint data in a cost-effective manner.
Reg Reader Research: SaaS based Email and Office Productivity Tools
Read this Reg reader report which provides advice and guidance for SMBs towards the use of SaaS based email and Office productivity tools.