Campus computer users--beware. On Dec. 13 a virus might strike your computer.

Residents of Leverett House were alerted last Friday that two computers in the House's computer lab had been infected with "W97M/Thus," a new virus that spreads through Microsoft Word files.

The virus threatens to delete the computer hard drives of owners who open infected files on Monday, Dec. 13.

According to campus computer experts, the virus is thought only to affect PCs and possibly only computers with Microsoft Word 97.

Rick Osterberg '96, with the Faculty of Arts and Sciences Computer Services, said the virus spreads through Microsoft Word documents. It infects the Microsoft Word program and also taints any documents saved with that copy of Word.

So if a student had opened a document on one of the infected House computers, then opened that document at home, the virus could be transmitted to the personal computer.

"Clearly, this is a destructive virus, if it lives up to its reputation," Osterberg said, referring to Dec. 13, when the virus is supposed to delete infected hard drives.

After the virus was identified with virus protection software, a Leverett User Assistant (UA) sent an e-mail message to all House residents warning them that the virus had almost certainly spread to some students' home computers.

The e-mail message advised students to update their anti-virus programs in order to test for the virus. It also provided cleaning instructions for students whose computers had already been infected.

Since then, the virus has also surfaced in Adams House, leading House UAs there to send an e-mail message to residents warning them of the virus.

Adams resident Malka S. Resnicoff '00, whose computer contracted the virus, said she was confused by these notifications.

"I heard from Adams House people that it affects the hard drive," Resnicoff said. "I also heard it could cause macro quirks."

A macro is a set of instructions that controls tasks within a given application or system. "W97M/Thus" is classified as a "macro virus," which means it causes damage with a set of instructions for a particular program.

Despite the confusion, Resnicoff said she followed the series of instructions presented in the e-mail messages from her UAs and quickly ridded her computer of the virus.

"It was really easy," she said.

Osterberg also stressed the importance of updating the anti-virus programs on students' computers. He said one such anti-virus program, Dr. Solomon's Anti-Virus Toolkit, is available for free use on FAS public servers.