We have been cut off from the internet a good part of yesterday and today. Some of our systems were infected by Trojans, and spam was generated via our backdoor.
A big lesson. Use as many malware scanners and busters as possible, redundancy in this area is not bad, it’s good! Use free ones and commercial ones, update as often as you can. Update the firewalls, install patches and service packs asap. CHECK WHAT THE CHILDREN ARE DOING! Ban all ‘free’ music sharing software. Punish everyone that sends chain mail and stupid office jokes, especially if it’s small applications. If you see friends of your kids pulling out USB-sticks from their bags, or CD-Roms with “fun stuff”, or “cool music”, or whatever, KICK THEM OUT! And only install applications if you are absolutely satisfied with the quality of the seller.
We did most of this and still it happened, so triple your effort on all the above. It has cost valuable time.
Even innocent tutorials on seemingly serious sites contained malware (in my case a turorial on isometric projection, and perspective, so where I expected it the least).