A security firm on Monday mistakenly identified a new Trojan as the first to exploit one of last week's vulnerabilities in Windows, but corrected itself and labeled it as one which attacks the same bug as August's Zotob bot worm.

Fanbot.c, said Trend Micro late Monday, included a proof-of-concept exploit against one of the vulnerabilities disclosed Tuesday, Oct. 11 in Microsoft's MS05-051 security bulletin. Trend also said that although the Trojan was written in Visual Basic -- which usually indicates low-level skills on the part of the attacker and often means it's a "script kiddy" copy-cat -- arming malware with yet another exploit matched earlier hacker habits.

By early Tuesday, however, Trend had modified its technical description of Fanbot.c to say that the exploit was actually one directed toward the Plug and Play bug unveiled in August's MS05-039 bulletin.

MS05-039's Plug and Play vulnerability was the one used by the Zotob bot worm to attack and infect Windows 2000 PCs worldwide.

Concern over a possible repeat of Zotob has been building since Microsoft released its October batch of bulletins and patches last week. One of the bug described in MS05-051, say security experts, could be easily exploited by attackers to launch another series of attacks against Windows 2000 machines.

This false alarm aside, no exploits against MS05-051 have been found; several exploits, however, have been created and disseminated by commercial vulnerability and exploit researchers to their customers.