Updated Websites operated by the US Treasury Department are redirecting visitors to websites that attempt to install malware on their PCs, a security researcher warned on Monday.

The infection buries an invisible iframe in bep.treas.gov, moneyfactory.gov, and bep.gov that invokes malicious scripts from grepad.com, Roger Thompson, chief research officer of AVG Technologies, told The Register. The code was discovered late Sunday night and was active at time of writing, about 12 hours later.

To cover their tracks, the miscreants behind the compromise tailored it so it attacks only IP addresses that haven't already visited the Treasury websites. That makes it harder for white hat-hackers and law enforcement agents to track the exploit. Indeed, Thompson initially reported that the problem had been fixed until he discovered the sites were merely skipping over laboratory PCs that had already encountered the attack.

The attack is most likely related to mass infections that two weeks ago hit hundreds of sites hosted by Network Solutions and GoDaddy, said Dean De Beer, founder and CTO of security consultancy zero(day)solutions.

He made that assessment based on the observation that the compromised Treasury websites are hosted at Network Solutions and the owner of grepad.com is also the owner of record for most of the websites used in the earlier attacks.

"There's a very high probability that it's the same person," De Beer said. "The only things that are changing are the domains."

Earlier, Thompson speculated the attack might be the result of someone exploiting a SQL injection vulnerability on the Treasury websites. After investigating that possibility, De Beer said it was unlikely because the hacked Treasury sites contained static HTML pages that aren't susceptible to such exploits.

Media representatives at the Treasury Department didn't return a phone call seeking comment. ®

This posting was updated to include details linking the attacks to similar mass compromises that hit sites hosted by Network Solutions and GoDaddy.