Did you know there are ways to capture information strictly from what is typed into your keyboard? Programs called keystroke loggers, or keyloggers for short, are nasty hacker tools that have the capability of stealing private information and passwords by capturing everything that is typed with your keyboard. While some companies and even parents have reported using keyloggers for monitoring purposes, a scammer (or an ex-boyfriend, girlfriend, or even casual “friend” who once had access to your computer) could use one to invade your privacy or steal your identity. They come in software and hardware form, and are not something to take lightly.
Physical keyloggers are easy to hide inside computers, and you would never know they were there. They can also sit on wires and cables, and if you don't know exactly what you're looking for, they can easily be missed. Fortunately, these external keyloggers are limited in what they can do, but their software counterparts are usually harder to detect and can do a lot more damage.
There are ways to prevent yourself from being victim of a keylogger scheme. KL-Detector is a small program that tells you if your Windows machine is infected with a software keylogger. It works by scanning your computer for new log files that a keylogger could be making. This free download pinpoints all programs that are creating those logs, so you can hunt down the keylogger on your machine. For a Mac, try reading the eHow article on the subject and follow the steps they suggest. Of course, many of your programs create logs, so you'll have to do some investigating. Look for programs you don't recognize and research them using Google. If you do find a keylogger, you will need to manually remove it. You can try security programs, but keyloggers are designed to avoid these.
To be truly safe, you might have to wipe your computer and reinstall everything. This is a last-resort option, but if you do have to wipe your computer, always make sure to back up your information first.