How to Know if Your Computer Has Been Tracked

There is no surefire way to know if your computer is being hacked or rootkitted by some cracker out there, short of keeping it cleanroom by never, ever connecting it to the Internet. However, there are many ways to distinctly reduce the chances of it being compromised.

Steps

1. Go into control panel, and choose add/remove programs. Uninstall any antivirus software you have currently installed (obviously, if you have antivirus software which you are happy with, then leave it installed). This is to avoid antivirus clashes which may render your computer unusable.
2. Secure your computer. If you already have a full antivirus suite, that is up to date and includes all of the following three components, then skip to step 8. Otherwise, for your computer to be secure you will need to download all of the following which you do not already have;
   • Install an antivirus scanner with real-time and heuristic scanning; Comodo BoClean and AVG Free work.
   • Install an anti-spyware scanner; HijackThis and Spybot S&D work.
3. Install a firewall to replace the weak windows firewall; ZoneAlarm works great.
4. Consider using intrusion detection software.
5. Install all of the required programs. Connect your computer to the Internet again, and allow them to update fully.
6. Run the antivirus scanner and anti-spyware scanners. If anyone has hacked your computer, the malware should be detected, and hopefully the software can remove it. Now your computer should be secure
7. Make sure to update your software frequently, at least once a week and you should be able to prevent nearly all attacks on your computer, provided you use your computer in a sensible manner.

Tips

• Use an alternative browser. Using Firefox or Opera as your web browser (or any browser other than Internet Explorer, which is infamously known as "Internet Exploder" because of its common malfunctions and vunerabilty to viruses) would result being targeted much less by viruses, as many are directed at Internet Explorer.

Warnings

• Never install something you have downloaded without fully reading the license agreement. Many newer malware programs are effectively legal as they are hidden or packaged with the desirable software and have a license agreement detailing their effects. If you see anything dubious in the license agreement, don't install. Pay attention to the "Agree" boxes when installing software. Blindly agreeing to everything presented can make cleaning out "added bonus" applications difficult, when it could have been much easier to "decline" when installing instead.
• Don't go to dodgy websites. If you search on google for something, and the description for one of the sites has a lengthy list of irrelevant and unconnected words in it, it's probably a sham site.
• Don't install activeX controls from a site you don't trust.
• Don't open E-mail "attachments" unless you have spoken to the trusted sender and they have verified that they included the attachment. Just because an E-mail originates from a friend, does not mean his / her computer hasn't been infected. The virus can spread by sending itself to everyone in the E-mail program contact list, often without the owner even knowing it is happening.
• Don't run applications or copy content from disks, thumbdrives, CDs, etc. that have been provided by others (including friends); or belong to you if they have previously been connected to another computer, unless scanned with your anti-virus program first. If an infected computer has accessed the data on the media, the data is likely to be infected as well.

Source: www.wikihow.com