1 - Never click on anything that pops up on your screen unexpectedly. Just right click on the application (usually it's Internet Explorer) in the Task Bar and select "Close" from there. Alternatively, press Alt and F4 simultaneously in order to close the active window. Still another alternative is to use Task Manager (Ctrl - Alt - Del) to close the offending program.
The reason for this is that the "bad guys" can make the window say anything that they want. For example, they can make the little X in the upper right corner of the window (normally used to close a window) actually install the bad stuff on your system.
2 - Don't ever, ever open any email! Yeah, that's a bit extreme - but the bad guys can fake an email from your best friend and you'd never know it until you checked with your friend.
So, always suspect emails with attachments - they're where most of the damage is done. It doesn't matter if it 's just a picture, or if it's a strange file that you have no idea about - they can all be infected with viruses. If you open one, make sure that your anti-virus and anti-spyware programs are running and scanning.
The best way is to "preview" your emails before opening them. Using web-based email, read the text before deciding if the attachment is from someone safe. For email on your computer, use a "screener" like the free program MailWasher (I like this one so much that I bought the Pro version). It'll allow you to read the first 20 lines of an email without downloading it - and you can delete the bad one's by using it's interface.
Edited by usasma, 17 December 2006 - 09:36 AM.