Worm outbreak feared after port scanning spike

A surge in scanning on a port associated with a Windows flaw patched last week suggests that a mass worm attack may be imminent, experts said.

A rise in activity on TCP Port 445 could be a sign that hackers are trying to exploit a flaw in Server Message Block, Gartner analyst John Pescatore said on Thursday.

"Increased scanning does not always mean an attack will happen but it greatly increases the odds that one will," Pescatore said. "I don't think this has a high probability of a worm but if people get lax about patching the odds of worms go way, way up."

Like would-be burglars knocking on doors looking for a likely target, internet intruders sometimes scan random computers to see if a particular network port is available, as a precursor to attack.

TCP Port 445 is used by SMB, which Windows uses to share files, printers, serial ports and also to communicate between computers. Microsoft recently released a fix for the "critical" vulnerability in the protocol as part of its monthly patch cycle.

Increased port scanning has preceded major worm outbreaks in the past, Pescatore said. Alfred Huger, a senior director at Symantec Security Response, also said a worm could be on its way.

Users should patch their systems as soon as possible, they both said.

However, Pescatore and Huger also noted port scanning by suspected hackers is common after Microsoft discloses vulnerabilities. Furthermore, this particular Windows flaw is not easy to exploit, so the scanning may not be an ominous sign at all.

Symantec saw a spike in scanning on TCP Port 445 last week but the probing of the port has since gone back to normal levels, Huger said. "I don't think we should be screaming the barn is burning by any means," he said.

Microsoft is not aware of any active attempts to exploit any Microsoft vulnerabilities via TCP Port 445, a company representative said on Thursday. Also, the software maker has not received any indication of malicious activity associated with the security vulnerability that affects SMB, the representative said.

Joris Evers writes for CNET News.com