New attack tactic sidesteps Windows security software

Computerworld - A just-published attack tactic that bypasses the security protections of most current antivirus software is a "very serious" problem, an executive at one unaffected company said today.

Last Wednesday, researchers at Matousec.com outlined how attackers could exploit the kernel driver hooks that most security software use to reroute Windows system calls through their software to check for potential malicious code before it's able to execute.

Calling the technique an "argument-switch attack," a Matousec-written paper spelled out in relatively specific terms how an attacker could swap out benign code for malicious code between the moments when the security software issues a green light and the code actually executes.

"This is definitely very serious," said Alfred Huger, vice president of engineering at Immunet, a Palo Alto, Calif.-based antivirus company. "Probably any security product running on Windows XP can be exploited this way." Huger added that Immunet's desktop client is not vulnerable to the argument-switch attacks because the company's software uses a different method to hook into the Windows kernel.

According to Matousec, nearly three-dozen Windows desktop security titles, including ones from Symantec, McAfee, Trend Micro, BitDefender, Sophos and others, can be exploited using the argument-switch tactic. Matousec said it had tested the technique on Windows XP SP3 and Vista SP1 on 32-bit machines.

Some security vendors agreed with Huger. "It's a serious issue and Matousec's technical findings are correct," said Mikko Hypponen, chief research officer at Finnish firm F-Secure, in an e-mail.

"Matousec's research is absolutely important and significant in the short term," echoed Rik Ferguson, a senior security advisor at Trend Micro, in a blog post earlier Monday.

Other antivirus companies downplayed the threat, however. "Based on our initial review of the public documentation, we believe this is a complicated attack with several mitigating factors that make it unlikely to be a viable, real world, widespread attack scenario," a McAfee spokesman said in an e-mail reply to a request for comment. "The attack would require some level of existing access to the target computer, as the attack described by Matousec does not on its own bypass security software or allow malware to run."

Kaspersky Lab had a similar reaction. "[We] have analyzed the published material and concluded that the issue is only linked to certain features of [our] products," Kaspersky said in an e-mailed statement. "Kaspersky Lab products implement not only [kernel] hooks, but a wide range of technologies, including secure sandboxing and other methods of restricting suspicious kernel mode activity."

Huger confirmed that attackers would have to drop malware of some sort on the targeted machine in order to utilize the argument-switch strategy, and that there are "lots of easier ways to game antivirus" than Matousec's technique.

"But that doesn't lesson the impact," Huger argued. "Actually, it would be really tricky to stop this, and gives attackers a strong opportunity to get around disk-based security."

Huger's greatest fear is that others take Matousec's findings, weaponize the argument-switch attack, and add it to one of the numerous underground exploit kits. "If someone packages this into an easy-to-use library, I think it'll be in play pretty quickly, with widespread adoption," said Huger. "Why wouldn't it?"