Google search results being redirected

Came across a vertually undetectable virus today that was randomly redirecting search results on google -for example, if you searched for “bt email” the number 1 result (btw website) would be redirected to an ask.com advertising page. I tryed all the usual stuff -an avg scan, a malware bytes scan and a thorough check with hjt, none of which found anything.

I also checked the hosts file, but there was nothing suspicious in there.

Finally I done an avg scan with the hard drive attached to another machine, and it turned out that atapi.sys, located in windows/system32/drivers, had been infected with a Trojan.

After copying the un-tampered atapi.sys file from another pc, the issue was resolved -this goes to show that hijack this can no longer be trusted to detect all viruses!!