What function does a key-logger perform?

A key-logger primarily performs the function of recording user actions, specifically capturing keystrokes entered on a keyboard, and then transmitting that information to a remote observer. This capability allows attackers or malicious entities to gather sensitive information, such as usernames, passwords, and other confidential data without the user's consent or knowledge.

Key-loggers can be implemented through various means, including software applications that run in the background or hardware devices that are physically attached to the computer. The information gathered can be misused for identity theft, financial fraud, or unauthorized access to personal and professional accounts.

The other options pertain to entirely different functions related to software management and security but do not align with the role of a key-logger. For instance, updating software focuses on keeping applications current, blocking malicious websites aims to enhance browsing safety, and cleaning temporary files is about system maintenance. These actions do not involve monitoring or recording user inputs.