As of 7 a.m. London time, Reuters PLC made its Reuters Messaging service available again to customers of the enterprise IM service.
Reuters PLC had suspended the messaging service early Thursday after a "handful" of Reuters Messaging customers began reporting infections from the worm, a variant of the Kelvir worm that has largely plagued MSN Messenger.
The worm, named Kelvir-Re by some security researchers, attempts to get users to download malicious code by way of a link included in a message. The worm replicates by sending the malicious message to contacts in an infected users contact list.
In a statement, Reuters said that the majority of its users stayed clear of the worm, though it did not provide an exact count of the number infected. Unlike popular consumer IM services such as AOL Instant Messenger, MSN Messenger and Yahoo Messenger, Reuters Messaging is a more controlled IM network largely used among financial services companies. It has about 60,000 users, including 16,000 at Reuters.
"The majority of Reuters customers run proper compliance, firewall and anti-virus protection and were therefore not infected," Reuters said in the statement.
Also, users of the most recent version of Reuters Messaging, Version 4.0, are immune to the worm, according to the London-based company. Version 4.0 is a free upgrade that has been available since October.
IMLogic Inc., which monitors IM security threats, also reported Friday that the worm had stopped spreading on the Reuters IM network and that the Web site distributing the malicious code had been removed.
"Due to Reuters rapid action, the Kelvir-Re worm was contained quickly and eliminated from the Reuters Messaging system," said Waltham, Mass.-based IMLogic, in a statement.