Researchers say they've devised a way to bypass protections built in to dozens of the most popular desktop anti-virus products, including those offered by McAfee, Trend Micro, AVG, and BitDefender.
The method, developed by software security researchers at matousec.com
, works by exploiting the driver
hooks the anti-virus programs bury deep inside the Windows operating system. In essence, it works by sending them a sample of benign code that passes their security checks and then, before it's executed, swaps it out with a malicious payload.
The exploit has to be timed just right so the benign code isn't switched too soon or too late. But for systems running on multicore processors, matousec's "argument-switch" attack is fairly reliable because one thread is often unable to keep track of other simultaneously running threads. As a result, the vast majority of malware protection offered for Windows PCs can be tricked into allowing malicious code that under normal conditions would be blocked.
All that's required is that the AV software use SSDT, or System Service Descriptor Table, hooks to modify parts of the OS kernel.
"We have performed tests with [most of] today's Windows desktop security products," the researchers wrote. "The results can be summarized in one sentence: If a product uses SSDT hooks or other kind of kernel mode hooks on similar level to implement security features it is vulnerable. In other words, 100% of the tested products were found vulnerable."