A computer code that spreads without the user interaction and can cause network performance problem is

Different categories of malicious software spread and behave in distinct ways, and telling them apart depends mainly on how they move from one system to another and whether they need user action to spread.

A computer worm is a self-replicating program that spreads automatically across networks from one computer to another without requiring any action from the user, such as opening a file or clicking a link. Because it copies itself repeatedly and travels through network connections on its own, a worm can rapidly consume network bandwidth and system resources, which is exactly why it causes network performance problems.

A trojan disguises itself as a legitimate, useful program and relies on the user willingly installing or running it, so it does require user interaction to get onto a system. Spyware is designed to secretly monitor and collect information about a user, and a computer virus, unlike a worm, needs to attach itself to a host file or program and typically requires a user to run that infected file before it can spread further.

Exam tip: the two features "spreads without user interaction" and "clogs the network" together point specifically to a worm; a virus needs a host file and user action, which is the key difference to remember.