Google is issuing warnings to people whose computers are infected with a type of malware that manipulates search requests.
A strain of rogue anti-virus software also includes a search hijacker component. The hijacker is designed to further enrich scammers by redirecting users of compromised machines through various dodgy pay-per-click affiliate sites instead of genuine search engines.
Instead of going straight to Google, surfers on compromised machines are sent via proxies. The traffic generated from malware-infected machines has an unique signature that has allowed Google to return warnings to victims using these machines.
The malware is programmed to ping a specific Google internet address from compromised machines. Google came across this when it took a server associated with this address offline during routine maintenance.
Legitimate search traffic was redirected, but the IP address still received thousands of requests per second, tipping Google off that something was amiss. Google security engineer Damian Menscher investigated the odd behaviour and discovered that it had been caused by a network of more than a million malware-infected machines, security blogger Brian Krebs reports.
Google is using the information it obtained to provide prominent warnings to potentially infected surfers that their PCs "appears to be infected", as illustrated by a blog entry here.
The warnings are something of a departure for Google, and may well help alert infected users that their machines are infected with a nasty cocktail of scareware and web-redirection malware. Unfortunately, it is probably only a matter of time before scareware scammers use fake templates from this new type of warning in attempts to peddle fake anti-virus software. Surfers are best advised to only purchase security software from recognised outlets and, in particular, to be suspicious of any warning that points you towards one particular product.
If in doubt, consumers ought to use a freebie scanner from the likes of Avast, AVG or Microsoft itself, at least as a first point of call.