A virus called "Little_Red.a," which prevents PC users from accessing Windows, recently infected the Harvard computer system through its main server, huscl.

All users who were connected to the server between 8 p.m. on December 18 and 8 a.m. on December 19 have potentially had their computers infected.

Campus authorities suggest that all computer users scan for the virus now with anti-virus software to protect their computers as well as Harvard's centrally provided user disk space.

Response to the virus has grown steadily as students returning from winter recess find their computers infected.

"There may be students who logged on right before they left, had their machines infected and then left without knowing it," said Frank M. Steen, director of Harvard Arts and Sciences Computer Services. Symptoms of viral infection include an inability to access or load Windows with a repeated response of "Missing/Unable to load" at the C:> prompt.

The virus probably originated from Harvard computers which were administering to the huscl server, since users don't have access to public areas on the server, Steen said.

"The reason this virus was unusual was because it affected a large number of people," said Daniel A. Lopez '97, president-elect of the Harvard Computer Society. Lopez, whose machine was not infected, said that more than 100 people have called HASCS to complain about the virus.

"All [the virus] does is tack on some extra information to each file and Windows refuses to operate because the file sizes are off. There's no hardware damage or data loss," Lopez said.

The issue of data loss is of primary importance to many students, particularly those writing term papers.

While users don't seem to have experienced any loss after getting rid of the virus, it may be too soon to evaluate the damage.

"To the best of our knowledge, there is no data loss," said HCS member Richard B. Osterberg '96. Osterberg said some files, such as win286.exe and winhelp.exe may need to be re-installed, but that it's impossible to determine the extent of the virus's effects at this time.

Anti-viral startup disks may be obtained from House User Assistants or from the Science Center Help Desk located in the basement of the Science Center.

The Freshmen Dean's Office also offers disks for Proctors to share with students. Anyone who picks up a disk should also take an instruction sheet which explains how to scan a user's hard drive as well as the M: drive on huscl.

Steen said he has also posted an explanation of the virus, its origin and solutions on two computer newsgroups, harvard.hascs and harvard.general.

"I had two 15 page papers due and I wasn't able to enter Windows," said Flora Tartakovsky '98, a Crimson editor.

"This is the first large scale virus problem that anyone can recall at Harvard," Steen said. "We have been fortunate in the past, and this one is easily correctable. It certainly will raise the level of virus awareness on campus.