Harvard students who thought they’d been sent party pictures from a friend earlier this week found themselves instead the unwitting perpetrators of a fast spreading—but relatively harmless—computer virus.

The virus, which infected computers around the world running the Microsoft Windows operating system, began spreading through Harvard e-mail accounts on Jan. 27.

Coordinator of Residential Computing Kevin S. Davis ’98, who is also a Crimson editor, estimated yesterday that the virus had infected about 100 Harvard students’ computers.

The virus arrived on computers as an attachment to an e-mail with the subject “new photos from my party!”

The infected attachment was disguised as a link to the website www.myparty.yahoo.com.

Computers infected by the virus quickly spread it to other computers, as the virus was programmed to send itself to everyone in the victims’ address books.

The virus causes no damage directly to infected computers, but does leave the victim’s computer susceptible to further hacking.

“It spreads really fast, and though it doesn’t crash the computer’s hard drive, it might have some serious side effects which we’re still not completely sure about,” said Muhammed H. Sultan ’05, a Harvard University Arts and Sciences Computing Services user-assistant.

In the future, Davis said, the virus could allow hackers to gain access to infected computers through the Internet.

Immediately after discovering the virus, McAfee—Harvard’s vendor for anti-virus software—made available on its website an update to its virus detection software to protect against the virus.

“Many people contacted us, and we helped them download the McAfee patch to get rid of the virus,” Sultan said.

Aaron M. Smith ’05, one of the Harvard students whose computer was infected, did not realize his computer was infected until his computer had already forwarded it to everybody in his address book.

“I saw the e-mail and clicked on the link to see the party pictures,” Smith said.

“Nothing really opened. I went to have a shower then and when I came back I had received about 50 e-mails from people on my mailing list telling me that I had forwarded them a virus.”

Most students were wise enough to delete the e-mail immediately, according to Davis.

“Students are much more computer-savvy now, so a lot of people didn’t open the attachment and deleted the mail from their computers,” Davis said.

—Staff writer Ravi Agrawal can be reached at agrawal@fas.harvard.edu.