A security company is warning IT managers and Web hosts to screen their content since cybercriminals are increasingly taking over legitimate Web pages to promote child pornography.

The victimized Web sites are being littered with posts -- containing offensive words and links to porn sites -- on forums and discussion boards designed to lure readers to various child pornography sites, according to an advisory from Sophos, Inc. The majority of the affected pages that the security company's researchers have found are on legitimate Web sites, and one is even on a site designed for children.

"What's most worrying about these posts is that they're happening on legitimate sites. Any Web site can fall victim to an attack, no matter what the content," said Fraser Howard, a principal virus researcher at Sophos, in a written statement. "This means that innocent Web surfers, including children, may stumble across this kind of offensive content. Every Web host must ensure that all areas of their site are fully protected and that all user input is carefully screened before it is posted on the site."

Sophos's researchers reported a recent upsurge in hackers injecting malicious code onto legitimate Web sites. These moves, they noted generally are focused on installing malware on victims' machines. Now attackers are posting content to sites to drive traffic to seedy, and often dangerous sites.

"Some of the same techniques that malware authors use in order to infect victims with malware are being used to distribute links and drive traffic to all sorts of Web content," said Howard. "The fact is that any unprotected Web site can be targeted by cybercriminals trying to spread their malicious content."

In March, Sophos had warned that hackers were luring users to a malicious site with promises of pornographic pictures. The widespread spam campaign was tricking users into downloading a spyware Trojan. The e-mails, which lure users with phrases like 'hot photos from my birthday', had fraudulent links to what they say will be online porn, but the links lead to a Web site containing the Troj/Pushu-A Trojan. Once it infected a machine, the malware tried to steal information from the PC's hard drive.

Sophos noted in its advisory this week that its researchers have reported the sites hosting these posts to the Internet Watch Foundation, the self-regulatory body that combats illegal content online.

Sophos is warning Web hosts to make sure they have up-to-date security solutions in place across their sites and that all user content is screened prior to posting. For businesses, Sophos recommends they deploy a Web filtering solution that not only filters based on Web site category, but that inspects the code of every Web site before granting access.