A stager is a small piece of malware designed to gain initial access to a target system and set the stage for more complex attacks. Its main function is to establish a connection to an attacker's server and then download or execute larger, more sophisticated malware payloads. Stagers are often used because their small size makes them harder to detect and analyze. By separating the initial access tool (the stager) from the main malware, attackers can bypass some security measures and increase the chances of a successful compromise.