The worm, called W32/Chet-A or "Chet", accompanies an e-mail with the subject "All People!" sent from the address [email protected]
The Chet worm is stored within an attached file named 11september.exe and is activated only when an e-mail recipient opens the attachment.
Like other e-mail worms, most notably the NIMDA worm that appeared last year and infected computers worldwide, the Chet worm attempts to use a computer's e-mail program and address book to spread copies of itself to other computer systems.
Worms can damage the computers on which they are run, or disable computer networks through massive copying and e-mailing.
Unlike the NIMDA worm, Chet does not appear to pose a serious threat to the systems it infects.
"This worm is not going to be a major problem," said Mikko Hyppönen, manager of Anti-Virus Research at F-Secure, which discovered the worm.
"There is a bug in the code that crashes the worm after it runs for a while."
The bug prevents the Chet worm from e-mailing copies of itself and generally leaves host systems unaffected, said Hyppönen.
"Some users may receive a Dr Watson report, but [Windows] and e-mail will continue to function," he said.
Despite its flawed code, however, the Chet worm is capable of infecting computers and replicating itself, Hyppönen warned.
"We found that under certain conditions, the virus was able to recover from its code error and continue running," said Hyppönen, adding that systems running the Windows 98 operating system and containing very long names in the Windows address book are particularly vulnerable to infection by Chet.
Makers of leading antivirus software rushed to post new virus definitions protecting against the Chet worm, despite the low risk posed by the worm.