Reuters has shut down its instant messaging system after a computer worm infected the network.
The worm, known as W32/Kelvir-Re, was first detected on the Reuters network early on Thursday, and the company suspended the service five hours later.
A spokesman for the company says that a handful of clients picked up the infection, which can switch between e-mail and IM networks and propagates by sending itself to all contacts in an infected user's address book or buddy list.
Reuters says it expects to restore service to users by Friday, after clearing the network of the worm. The infection does not attack end-user software, but its presence can seriously slow down network throughput.
The virus is an embarrassment to Reuters, which claims more than 60,000 users for its Microsoft-based instant messaging system. The spread of the worm is likely to shake user faith in the security of the network as a trusted, closed community.
Reuters has advised customers to contact their anti-virus software providers and obtain the latest signatures for the virus, which appears to be a new variant on an infection that began circulating earlier this year.