What is a Keylogger?
Keyloggers are an extremely dangerous member of the malware family. As their name implies, they log and record every key you press while on the computer and then send this valuable data back to the attackers. This means that as you log in to your various accounts, the attackers will capture your username and password for each one. With a keylogger in place, a short computer session could end up compromising your online banking details, email, social media, as well as other important accounts.
If you re-use the same password between multiple accounts and you are infected with a keylogger, then those other accounts are also in danger even if you didn't log in to them while the keylogger was use. The attackers will attempt to use the passwords and usernames/emails that they recorded using the keylogger on other popular websites and services. If they find a service that uses the same email/username and password, they will be able to fraudulently log in to that service as well.
There are limited cases where keyloggers may be used in a legitimate manner, such as to monitor your children's online activity. This would allow you to see the things that your child is typing while using the computer.
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