More than a week after Microsoft patched 10 security flaws in its software, security experts are offering differing views on whether an attack that exploits one of these flaws may be brewing.

On Tuesday, research firm Gartner published a report warning that a vulnerability found in Microsoft's SMB (server message block) file-sharing protocol could be used in a new attack. Because security vendors had noticed a rise in activity relating to the TCP/IP port 445, which is associated with SMB, Gartner concluded that a "mass attack" could be in the works. Ports are special numbers used by the Internet protocols to route messages to different applications.

Gartner recommended that users apply the Microsoft patches as soon as possible and ensure that port 445 was blocked via a firewall.

Other security experts, however, were doubtful that a port 445 attack was imminent.

Port 445 has already been used by so many other attacks, including the Sasser and Nimda worms, that even if a new worm were to be created, it would probably not change things, according to Russ Cooper, senior scientist at Cybertrust and editor of the NTBugtraq discussion list. "The people that have 445 exposed and therefore would be vulnerable to attack by last week's exploit, will likely already have been compromised by anything that's been going around for the last three years," he said on Thursday.

Cooper was dismissive of reports of a possible port 445 attack. "People are desperate for something to happen in the security space because it has been so long (since a major attack)," he said. "I think the reports are hype."

A researcher with Symantec, which first noticed the bump in 445 activity last week, generally agreed with Cooper's assessment.

"There were several vulnerabilities that came out," said Alfred Huger, senior director of engineering at Symantec Security Response. "This was probably the least severe of those that came up, and it's probably the hardest to exploit."

Users who have a firewall or a router that blocks access to port 445 are unlikely to be affected by the SMB bug, even if they haven't installed Microsoft's latest patches, he said.

Huger believes that another of last week's vulnerabilities, relating to the PNG (Portable Network Graphics) image format, was much more likely to be the source of a widespread attack. Using this exploit malicious code could be inserted in something as innocuous as a banner ad, he said. "They could break into your computer without you even knowing it," he said.

The IDG News Service is a Network World affiliate.