how likely is it for a virus, malware, or spyware to come from these major websites?

[Alyssa]

My uncle has a desktop, and is completely anal about where we go on it. He doesn't like me going on anything. He thinks horrible stuff will come from these sites:
Yahoo(for email and Y!answers)
Facebook
Youtube
google(gmail)

I know not to open spam email, and the computer is protected, and I never click on ads. It's getting ridiculous. I can't even check my email when he is in the house anymore!

[needtoknow]

Very unlikely as far as I'm aware.
These major companies have pretty good security systems in place but there are additional sites that are imbedded as advertisements and these may lead onto other sites containing malware etc.. that you do need to be careful of. Tell your uncle not to worry too much but I would recommend that you get an anti-virus software installed just in case something did happen

[Al Scusi]

Ask your uncle which software you need for a firewall, anti-virus, and anti spyware.

If he replies quickly then check online if other recommend the same packages then download and install your choice.

If he is slow in replying or does not know then tell him you have a Friend who you can ask for help to protect your machine. At least one of your friends is likely to know how.

Meanwhile my recommendation is that you download and install Malwarebyte; Zone Alarm; SuperAntiSpyware and a good anit virus package like AVG.

These products will keep most stuff off your system and if set up carefully the Zone Alarm will stop your machine from being so obvious to hackers.

Additional: Nearly forgot! If protected properlty there is not much chance, without it there is a high chance but not on reputable sites and as long as you don't click on links in Questions and Answers that take you off Y!A

[Chris G]

Very unlikely if you're careful what you open or click.  If he's really paranoid, tell him to install the freeware Sandboxie, and everything that happens on the computer while it is open happens in a remote 'sandbox' that gets fully deleted when it's closed.

http://www.sandboxie.com/