Feeds

Stealth encoding bypasses IDS protection

Attack technique gets in under the wire

  • alert
  • submit to reddit

Choosing a cloud hosting partner with confidence

Cisco's Intrusion Detection System (IDS)is not the only technology that fails to protect IIS Web servers against stealth unicode attacks.

An advisory by eEye Digital Security, reports that network and server sensors from ISS, Dragon Sensor 4.x, Snort (prior to version 1.8.1) and components of Cisco Secure IDS are affected by the issue. Symantec and Network Associates have stated that their products are not vulnerable.

Links to patches and advisories from vendors affected by the issue have been collated by Security Focus and can be found here.

Last week we reported that Cisco had to alert its customers about the problem only a day after announcing enhancements to its Secure IDS products.

In fact the non-standard method of encoding Web requests (called '%u'), which Microsoft's IIS supports but an IDS fails to decode, can allow the creation of an attack which bypasses the IDS set-ups of most vendors.

In practice, this means an attacker could modify a web-based attack, such as a "stealth" Code Red, so that requests are encoded with '%u' Unicode encoding, in order to get around IDS protection.

The obfuscation method works only because Microsoft's IIS permits a non-standard decode of html (so Apache servers, for example, are not affected).

It's worth remembering that avoiding IDS detection is only the first stage in an attack. The second stage - the compromise of the ISS Web server - is where the damage is done. Webmasters can easily stop such an attack by use of the latest security patches. But as we know, many companies are ill-disciplined in applying security patches as they come out.

IDS products, which inspect network traffic and raise alerts over suspect packets, are used for the secondary protection of IIS Web servers, so making sure they aren't fooled, still merits attention. ®

Related stories

The Cisco Intrusion Undetection System
Code Red and the Cisco Side Effect
Security software crashes Cisco kit

Top 5 reasons to deploy VMware with Tegile

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

Why and how to choose the right cloud vendor
The benefits of cloud-based storage in your processes. Eliminate onsite, disk-based backup and archiving in favor of cloud-based data protection.
Forging a new future with identity relationship management
Learn about ForgeRock's next generation IRM platform and how it is designed to empower CEOS's and enterprises to engage with consumers.
Designing and building an open ITOA architecture
Learn about a new IT data taxonomy defined by the four data sources of IT visibility: wire, machine, agent, and synthetic data sets.
How to determine if cloud backup is right for your servers
Two key factors, technical feasibility and TCO economics, that backup and IT operations managers should consider when assessing cloud backup.
High Performance for All
While HPC is not new, it has traditionally been seen as a specialist area – is it now geared up to meet more mainstream requirements?