A new version of the Santy worm appeared over the weekend, and according to analysis done by some security firms, poses a broader threat than its ancestors, which used Google to spot vulnerable Web bulletin boards, then defaced them.

Dubbed Santy.e, the worm differs significantly from its predecessors, said Moscow-based Kaspersky Labs in an alert. Rather than target only those Web sites running phpBB, software for creating Internet forums using the PHP scripting language, the worm can exploit any site that's left allowed arbitrary file inclusion into PHP scripts.

"This can only be prevented with decent, secure coding," said Kaspersky Labs. "Every site [that uses PHP] is potentially in danger."

Kaspersky noted that it had already received reports of Websites attacked by infected systems, and that some servers have been compromised or dramatically slowed down as their loads climbed under constant probing.

Like earlier Santy variations, Santy.e uses Google to identify exploitable Web pages written in PHP which use the vulnerable functions "include()" and "require()." Santy.e, however, also throws Yahoo's and AOL's search engines into the mix, learning a lesson from the originals, which were stymied when Google blocked their searches.

Another anti-virus firm, the Finnish F-Secure, downplayed the threat, saying "in practice these latest variants haven't gotten out of control." F-Secure credited that to the fact that the Brazilian group suspected of being behind the attack is using a relatively small number of PCs -- about 100 -- in the bot network that's searching for vulnerable sites and then launching attacks on those it finds.

"While there are lots of vulnerable sites out there, this worm is still under control," F-Secure said in its online warning.

However, because the vulnerability lies in poor programming techniques rather than a code bug, securing sites against the Santy.e exploit may be time-consuming, and require rewriting scripts with the include() and require() functions.