[15Peter20]

Can somebody hack your computer, send you a trojan or in any way get to monitor your online activity by adding you and looking at your Facebook profile?

[Justawind]

I am *guessing* it would be possible but unlikely.

[lunarlander]

If they are just looking at your profile then nothing bad can be done. Infections can occur when you go a hacked website, or download infected things.

For example, Flash v7 has a vulnerability that allows a hacker to run code on your computer. If you visit a site that has a hacked flash file, when you view it, the hacker's code will execute and infect your machine, install keyloggers and other monitoring software. So becareful where you surf to. There is a program call Site Advisor that places ratings beside every Google search result indicating whether its a bad site, I always advise people to use that.

If you download and run a program on your pc, that program can do anything - set up backdoors, install keyloggers, and infect your pc. This is where your antivirus program can come to the rescue. They are not perfect and cannot protect against the lastest viruses, but its better than nothing.

[Jack1000]

Just be looking, no. The same with stuff like My Space. But downloading any prompt or attached file within a page, could bring malware to your system. You can go to your profiles in both of those settings and change/customize the privacy settings to exactly what you want.

Jack

[BlueEyedFox]

The simple answer, No. Do not worry. Just do not downlaod anything on the Facebook that the person may have linked or a clickable picture or such.