Google's popular, free weblog hosting service Blogger.com appears to have been infiltrated by a spam e-mail ring that is setting up fake blogs, according to a security company.

In an advisory posted to its website, Fortinet Inc. of Sunnyvale, Calif., said malicious computer scripts that redirect people to a phishing site called Pharmacy Express — which purports to be an online pharmacy — have appeared on hundreds of blogs.

Another script sends visitors a single-pixel image that tracks details of their browser's information.

The Pharmacy Express phishers are also driving traffic to its fake blogs and on to its phishing site through a mass e-mail worm known as Stration.

The company also discovered that apparently legitimate blogs had been infected with malicious code, pointing to what appears to be a motorcycle fan site as an example.

"The site, seemingly created by a Honda CR450 enthusiast, now infects visitors with the Wonka Trojan," Fortinet said.

Fortinet have given the threat its fourth-highest severity ranking on a five-point scale.

The company also warned about other popular subjects that are likely to be linked to maliciously crafted or infected blogs.

"Other popular topics commonly linked to malicious blog sites include Star Wars, school, furniture, Christmas, cars and girlfriend," Fortinet said.

Google spokespeople could not be immediately reached for comment.