A little-known capability in Google’s search engine has helped security vendor Websense uncover thousands of malicious websites as well as several legitimate sites that have been hacked, the company said Friday.

By taking advantage Google’s binary search capability, Websense has created new software tools that can sniff out malware using the popular search engine. Websense researchers Googled for strings that were used in known malware like the Bagel and Mytob worms and have uncovered about 2,000 malicious websites over the past month, according to Dan Hubbard, senior director of security and research with Websense.

Though Google is widely used to search the Internet for webpages and office documents, the search engine can also peek through the binary information stored in the normally unreadable executable (.exe) files that are run by Windows computers. "They actually look inside the internals of an executable and index that information," Hubbard said.

Hubbard and his team plan to share their Google code with a select group of security researchers, but they will not make the software public, for fear that the tool could be misused by the bad guys.

Virus authors, for example, could use the Websense software to search for worms and viruses to use in their attacks, Hubbard said. "Instead of buying them on the black market, [an attacker] could search for them and download them on his own."

Some bloggers have pointed out that hackers might also be able to manipulate the binary search feature to trick Google users into downloading malicious software.

Hackers could add common search terms into their malicious code in order to be included in search results, for example, which would then show up alongside legitimate websites.

Google has seen this happen "on occasion," and is making an effort to shield users from this malicious software, a Google spokeswoman said.

This type of attack wouldn’t work unless users clicked on the standard Windows prompt saying that they want the executable code to run on their systems.

And this is something that most Web surfers are smart enough to avoid, according to Johnny Long, a security researcher with Computer Sciences.

"I think the ‘tricking your browser into running an executable file’ trick is a little old," said Long, who wrote the book Google Hacking for Penetration Testers. "There are other more elegant attacks to worry about."

The most interesting thing about Google’s binary search capability is not its security implications, Long said, but the fact that it shows that Google may be thinking about becoming a file-searching service.