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By | Dan Goodin 21st December 2007 03:05

Anti-virus protection gets worse

What is this thing you call heuristics?

Antivirus software is getting worse at protecting users from new threats, according to two reports which found malware authors are getting better at disguising their creations.

German computer magazine c't studied 17 antivirus programs and exposed them to completely new samples of malware. What they found wasn't encouraging. Detection rates sank to 20-30 per cent, from 40-50 per cent in a similar test last year.

The c't researchers also created variants of known viruses and found that virtually all of the scanners missed at least some of them.

Plenty of questions remain about the report, which is scheduled to be published in January. (Heise has a brief synopsis of the report here.) It would be helpful to know the methodology and what products were tested.

But taken at face value, the research raise questions about the effectiveness of heuristic engines. Heuristic scans examine the code inside a file for suspicious behavior and flag those it thinks have a high likelihood of being malicious. Because they don't need virus definitions, they can provide better protection immediately following the release of a new virus.

A second report, released Thursday by researchers from Kaspersky Labs, said online scanners may be contributing to the deterioration of heuristics. Sites such as VirusTotal, for instance, allow a user to scan a suspicious file. The site then compares the code against 32 antivirus products to check for malicious code.

"But as so often happens, something that can be used for good - helping users check the integrity of their files - can also be used by virus writers," the researchers note. "They quickly caught on to the fact that services like the ones mentioned above could be used to test how well their creations can evade popular antivirus solutions."

They document websites such as, which charge as much as a dollar per scan and promise not to submit the files to antivirus companies. That way, malware developers can be assured their works in progress won't be sent to antivirus companies.

Bright spots in the c't report: Eset's NOD32 detected 68 per cent of the completely unfamiliar attacks. And F-Secure was "able to perform convincingly in the behavioural blocking test", which measured how well a product protected a machine from getting infected. Kaspersky and BitDefender also got high marks. ®

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