How to Tell If Hackers Got Into a Computerby Shiromi Nassreen
As essential as the Internet is to many computer users, it does come with some dangers--primarily the ability of a hacker to hack into your computer, plant Trojans and viruses and steal private information. Luckily, there are a number of ways to tell if your computer has been hacked. Unfortunately many of these checks only work if the user has taken some preventative steps to begin with.
Look for irregular activity on your computer. Irregular activity includes your computer suddenly running very slowly even though you are not doing much on it. You may have noticed documents missing or misplaced, or an email that has been sent out by you that you don't remember typing. Perhaps your computer restarts for no apparent reason. These are all signs your computer's security may have been compromised.
Run a full, system-wide file check. Search for recently modified system-wide files. You can do this by using a free utility program like NIS File Check. These system-wide file check programs run the program when you know the computer is clean. The program creates a database of your clean computer. When you suspect your computer has been hacked, you run the program again. The program compares the two databases and notifies you of all changes made to your system files.
Get a spyware program. Running a full, system-wide check can be time-consuming. If you would rather have a program that will do these tests for you on a regular basis, consider getting a spyware program. Spybot Search & Destroy and Ad-Aware are two popular free programs.
Run a port scan. Most Trojans must wait for connections from the hacker (so the hacker can control the program), and must listen in on a port. Use a program like Fport or TCPview to view what programs are currently running and listening in on your ports. That way, you can look for suspicious-looking files and delete them.
If you would prefer to have a program listen in to your ports for you on a regular basis, consider getting a firewall program. Zone Alarm is one popular program. A firewall program will not only listen in to the ports, but will notify you of suspicious activity. You can set it up to only allow certain programs to access the Internet.