Popular US gadget blog Gizmodo apologized to its readers on Tuesday after being duped by malware masquerading as an advertisement.

- Guys, I'm really sorry but we had some malware running on our site in ad boxes for a little while last week on Suzuki ads - Gizmodo editorial director Brian Lam said in a message at Gizmodo.

- They somehow fooled our ad sales team through an elaborate scam - he said. - It's taken care of now, and only a few people should have been affected, but this isn't something we take lightly as writers, editors and tech geeks.

- Be careful, load up some antivirus and make sure your system is clean - Lam advised.

The New York Times website recently fell victim to a similar attack in which users who clicked on a pop-up box were directed to go to a site that claimed to offer anti-virus software.

The site was itself virus-like, hijacking a Web browser and making it appear as if a scan for viruses is running, the Times said.

Web security firm Dasient estimated meanwhile that more than 640,000 websites were infected with malware and said  -attackers are focusing more than ever on compromising legitimate websites and using them to distribute malware. -

Dasient, in a blog post on Tuesday, said it had identified more than 52,000 Web-based malware infections in the third quarter of the year.

- One of the challenging things about trying to protect sites from the threat of Web-based malware is that the attacks often evolve very quickly and make use of a number of obfuscation techniques to evade traditional malware scanners - it said.