Go here first and read:
http://www.betaone.net/forum/article.php?a=3
If you have not always been using a firewall that rerports which apps are trying to connect to the internet, then you may have had a keylogger and trojan combination for quite sometime and never knew it. At the same time you need to have been scanning your system for such nasties as those all along.
Just scanning with a virus scanner is not enough anymore as new ones are made daily just to get around someones security programs.
All that you can do now since that all mail is back to normal is clean all computers of all bad things there. This is what I would do.......
1 Format all computers there by writing 1's and 0's to the drive, check the drive
makers direction as to the correct way for each type of drive.
2 Get a firewall that will tell you when an app is connecting out.
3 Get a trojan scanner that will have constant updates
4 A scanner for malware, example...AdAware and there are others
Now that you have a machine with all of the above plus other protection that others here can name, connect the computer to the internet just long enough to get all the things installed from GOOD sources and updated. Then disconnect from the internet.
Then spend several hours scanning your previous backups as well as ALL programs you may have burnt to cd or dvd as a backup....be sure to scan these for problems. When all cd's are scanned you can then install to the other computers.
Watch the firewall and when a program ask for a connection be sure you know what the program is first before allowing it.
If you have a router there is a log file in there that will tell about incoming and out going connections.
Thanks
Dudelive