Behavior-based detection involves monitoring the behavior of a file or program while it is running and looking for any suspicious activity. This can include things like attempting to access sensitive system files, making network connections to known malicious servers, or modifying other programs or system settings without the user's permission. Behavior-based detection is generally more effective at detecting unknown threats than signature-based detection, but it can also be more resource-intensive, as it requires continuous monitoring of the behavior of files and programs on the system.