something strange happened last night. i was on msn messenger, within 5 seconds my friend logged in and sent me a link. the link informed me you could check who had blocked you on msn messenger. just as qucikly he went offline. foolishly i clicked on the link and entered my hotmail address and password. nothing happened. i received a message saying the server was too busy. i thought nothing of it. however last night i signed onto msn messenger and my friend told me 'that link you sent me, it's a virus', 'what link???' i replied confused. 'i didn't send you no link, i haven't even been online i've been at work all day'... what is going on?

i have been reading about spyware/adware. some people say it's impossible for a mac to catch but in the articles i read online apparently macs can get these things. i asked my flatmate about it since she studied computer science. she said i should try and get my mac better protected. but i'm really only a novice when it comes to such things. i have an outdated version of norton anti virus. i'm running a mac os x 10.3.9. should i be running a firewall? does this not come with the norton anti virus? do i have to download it separately? any pointers in the right direction would be gratefully accepted. cheers.

My guess would be that you've been infected with some sort of Mac MSN Messenger worm -- apparently it's sending out messages with a link to the worm to infect people on your contact list. First of all, stop using MSN immediately, for two reasons: a) you don't want to infect other people, and b) you don't want to spread or make the infection any worse for yourself.

The second thing you should do is start cleaning out anything MSN-related:

• /Applications/Microsoft Messenger
• ~/Library/Preferences/Microsoft (entire folder)

Deleting all of the above should get most of it. It wouldn't be a bad idea to scan with Spotlight for any other MSN-related files.

Thirdly, you should install some sort of antivirus software, if just to ensure that you've disinfected your Mac. Probably the best free one available for the Mac platform is ClamXav, so download that one and scan your hard drive. Some good commercial software include Norton Antivirus by Symantec and VirusBarrier by Intego. Both are very high quality and have received very praising reviews in magazines such as MacWorld.

Once you're confident that you've completely disinfected your Mac, go ahead and re-download MSN Messenger.

Update: I got this link sent to me in MSN the other day, too. it actually has nothing to do with your computer -- I'm guessing it's simply a phishing site that uses your Windows Live password to send links to people on your contact list. The long and short of it is, you need to change your MSN password ASAP.