What is a keylogger, and why should you be concerned as to whether or not your computer is infected?  Keyloggers are spyware programs that record everything that you type on your computer's keyboard.
  The person that placed this malicious software on your PC can later retrieve this info and consequently discover your passwords, user names, account numbers, and other sensitive data.
They can gain knowledge of your web surfing habits, and even read your emails.
Yes, key loggers are a very powerful software application that can literally steal your identity.
Keyloggers have become very sophisticated.
They have the ability to record keystrokes even if the user is logged off.
They can run silently in the background, invisible in the process list, and virtually undetectable.
They can spy on active applications, taking text snapshots of them.
Some key loggers can be turned on remotely.
  How does your computer become infected with this key logger software?  If you download music, software, or just about anything else from the Internet, it could contain a keylogger or other spy ware or adware.
It could enter as an attachment to an email you receive.
There are some legal, ethical, and truly beneficial ways that keylogger programs can be used.
For example, parents can keep an eye on their children's online activities, thus protecting the kids from distasteful content and even predators.
  So how do you avoid becoming infected, and what if your computer is already compromised? Only download music, software, etc.
from trusted sites.
Do not open email attachments unless you know that they are clean and safe.
 Invest in a quality anti spyware software to remove the keylogger and protect from future infections.