Many users of the MSN instant messaging service have received messages from friends lately with subject lines like "How drunk was I in this picture?" "Did you take this picture?" and "Is that your mom in this picture?" and containing an attachment named img807.zip.
The file contains a virus that if opened will either freeze the computer or begin to open files uncontrollably. When the computer is forcibly turned off and then turned back on again, the virus will continue by sending copies of itself to all MSN contacts.
Chien Sheng-tsai (簡勝財), a technical support manager at Trend Micro (趨勢科技), said that viruses such as this appeared on instant messaging services such as MSN, Skype and Yahoo several years ago, and the rate of infection was quite high because the viruses came from friends. This type of virus -- called a "social virus" -- became even more common about a year ago.
Once a virus has infected a computer it will send out large volumes of messages and may even plant a Trojan horse or spy program in the computer, he said.
Advanced technology has made it possible for the computer to continue to function normally so users are not even aware that the computer has been infected, thus increasing the risk.
As a result, Chien said, users should be on their guard even when the sender is a friend.