University of Iowa freshman Cailie Furlong was studying online Wednesday — until she was blocked from the UI network.

Her computer, along with around 350 other Mac computers on campus, had been infected with the Flashback virus.

UI Chief Information Security Officer Jane Drews said computers received the virus from an infected website. Once installed, the virus allows its creator to access personal information such as account passwords.

"It’s something to take seriously," she said.

Concern has been serious enough for the UI Information Technology Services to block infected Macs from accessing the campus wireless network. The UI’s intrusion-detection system detects the Flashback virus — which accesses computers by exploiting a security flaw in Java — by catching the network activity of machines trying to access botnet, a network of hacked computers.

Dehio said he was surprised by the block.

"I think the university should send out an email before it kicks you off the network," he said.

Drews said some students with Macs should take precautions by getting the most current operating system — OS10.7 — and running software updates, installing antivirus software, and turning on firewall programs.

Because reformatting deletes everything on a computer, UI computer-science Associate Professor Doug Jones recommended students back up any important information.

"In general, the important thing to do is keep backups of anything that matters to you," he said. "[Because] a good thing to do if your computer does get infected is to wipe everything."

Cases such as the Flashback virus represent a decrease in antivirus effectiveness over the past few years, Jones said — especially for Macs, which are not considered as vulnerable to viruses as PCs.

"It’s sort of disturbing that Macintoshes are being targeted now," he said.

Drews said Apple released a software update Tuesday to prevent Mac computers from being infected by the virus. UI ITS is testing the software to see if it clears the virus completely, she said.

If the software is effective, she said, the university will take that approach instead of reformatting and reloading infected computers.

Furlong said UI computer services were able to save all her documents and pictures, but everything else was gone.

"I couldn’t do my homework last night," she said. "I couldn’t even work in the ITC because it is all saved on my laptop."

Dehio said he completed all of his homework earlier in the week but was still concerned about the virus spreading around end-of-semester deadlines.

"I’m losing the time that I should be studying and researching for my essays," he said.