Final answer:
A keylogger is a malicious software that records every keystroke and sends the data to a hacker, posing a significant threat to personal and financial information.
Step-by-step explanation:
The malicious software that captures every keystroke and sends it to a hacker is known as a keylogger. This type of software runs stealthily in the background of a user's system, recording all keyboard input, and may transmit the data to a third party without the user's knowledge. Often used for identity theft or to compromise online accounts, keyloggers can be a significant threat to one's personal and financial information. To solve completely the issue of a potential keylogger, it is important to use trustworthy antivirus software and keep all systems updated with the latest security patches.