To go online is to live dangerously. Aside from the risk of viruses, there are also worms and Trojan horses -- all trying to find an unsecured computer upon which to work their mischief.
Check out also:
- http://gustmeesen.wordpress.com/2012/03/16/beginners-it-security-guide/
- http://gustmeesen.wordpress.com/2012/02/13/why-ict-security-why-the-need-to-secure-a-computer/
- http://gustmeesen.wordpress.com/2012/01/05/pc-security-howto-secure-my-pc/