It is a testing code which checks if the system is exploitable or not by a given vulnerability. Generally after scanning, the hacker do not immediately attack the system with an exploit because if the exploit did not work, the target might get to know that something malicious is going behind the scenes. So to be a clever hacker, the attacker uses an Auxiliary and after it gives a green signal, the attacker exploits the target. In this sense, an auxiliary acts as a helper for the exploit.
Debugging Myths About CyberSpace!