Answer: Self-replicating
Explanation:
A worm is a self-replicating type of virus. It enters the network by exploiting the vulnerabilities. The self-replicating nature allows it to move quickly from one computer to other. Due to this feature the worm is able to propagate and spread in multiple system and also have a potential to affect systems worldwide.
It does not enter through a file or program but through of network vulnerability.
