Let me attempt to clarify the situation with 'Flashback' (or 'Flashfake' according to Kaspersky).
There are reportedly 14 different variations of the Flashback malware. The first 13 versions were Trojan horses. The most recent version (listed as Malware.OSX.Flashback.N by Intego, and .K by some others) is the one that became famous, the one that uses what was an unpatched Java exploit, able to use a drive-by infection to install the initial malware package without any user password permission. That security hole was patched by Apple in their recent series of Java updates for Mac OS X 10.6 and 10.7. Also available to 10.7 users who never installed Java is Apple's Flashback Malware Remover app.
MEANWHILE: The previous 13 variants are still around and people may well continue to become infected. Also, Apple's Flashback Malware Remover (10.7 only) does NOT remove all variants of Flashback. It only removes 'the most common variants'. Therefore, even after running Apple's Remover tool, you may STILL be infected with a variant of Flashback.
How does the school know you're infected? The most likely answer is that they see your specific IP address performing behavior characteristic of the Flashback botnet. ALL variants of Flashback install bot malware onto your Mac and connect it to the overall Flashback botnet. There is a set group of IP destination addresses being used by the Flashback botnet. If your computer is regularly connecting to one or all of those IP addresses, you're infected.
What ELSE can you do to detect and kill off the Flashback malware? There are a number of FREE malware detection programs. Some of them include malware removal tools as well. I suggest you try both of the following:
1) ClamXav. This is a free program that makes use of the ClamAV open source project. Mark Allan provides a Mac GUI on top of ClamAV that makes it easy to use and schedule. You can read about it and get it here:
http://www.clamxav.com/
I am involved with a number of people interested in Mac security who do our best to keep ClamAV up-to-date with the latest Mac malware definitions.
2) Sophos Free AntiVirus for Mac. Sophos writes anti-malware software for small business and enterprise Mac users. But they also offer this free tool that is kept automatically up-to-date with the latest malware definitions. You can read about it and get it here:
http://www.sophos.com/en-us/products/free-tools/sophos-antivirus-for-mac-home-ed ition.aspx
Both of the free anti-malware tools include removal of malware. Just be certain to keep them up-to-date at all times.
If you would like a full featured, bells and whistles commercial anti-malware program, the best IMHO is Intego's VirusBarrier X6. I own it, use it and like it. They offer a full featured 30-day trial version here:
http://www.intego.com/demo
VirusBarrier costs $50 with charges after the first year for further malware definition updates. You can currently purchase it for $40 via CNET here:
https://www.trialpay.com/cart/?pp=DfSfSo8P&c=7a328be
Take your pick of these three. They all can remove all the variants of Flashback and get you off the Flashback botnet.
:-Derek
