Change your passwords frequently. Recommended at least every 180 days.
Use a screen saver that adds password protection when you are away from your computer.
If MSIS is not managing your anti-virus software, then keep your anti-virus software current.
Log off the network and your e-mail account if you leave your computer running overnight.
Promptly remove printouts of sensitive information from the printer.
Software manufacturers provide information almost daily on flaws they have fixed. For Windows users, an authoritative site, Microsoft Security Advisor, is available.