Security
The first step you need to take to keep your computer safe is to keep it updated with all the Microsoft patches. You also need to be very careful about what applications you install onto your computer.
Keep all the application that you use to access the internet up to date. Most applications automatically let you know they need updated. You can also check for new updates on the Help Menu of most modern applications.
As a rule you should not run any attachments you receive in your E-Mail, especially if you are not expecting one. Especially if they are executable files (.exe)
Virus Protection
Have a Virus scanner like AVG running all the time on your computer. Do complete system scans periodically and keep your virus protection up to date.
Be Careful when you click on Links
Make sure the link is taking you where it says you it is. For instance look at the status bar at the bottom of your browser when the mouse moves over a link to make sure its a good link
Move the mouse over this link to see if its a good link
Legal Scams
Not all scams are illegal. And not all large internet sites are reputable. For example imagine you buy products off firms like buy.com, classmates.com, expedia.com, hotels.com as well as others. These are large supposedly reputable firms. OK, all these sites talk users credit cards details. That's ok. But guess what they do. They allow a pop-up to appear that has large letters saying something like Join our Loyalty program. There is fine print with details telling you it costs $10.00 month or what ever. But you do not fill in any credit card details, so you are not really warned. All they ask for is your E-Mail address. From then on you get a recurring payment off your credit card.
Read the Cnet Article
Leo goes into great depth in http://twit.tv/222 approx 6 min into show.
