In CEH v13 Module 06: Malware Threats, a worm is described as a self-replicating piece of malware that spreads independently from one system to another without needing to attach itself to any file or program (unlike viruses).

Key Characteristics of Worms:

Capable of network propagation without human interaction.

Often used in mass attacks (e.g., WannaCry, Conficker).

Can cause significant damage by:

Consuming bandwidth.

Spreading payloads (e.g., ransomware).

Modifying or deleting files.

Option Clarification:

A. Rootkit: Hides presence of malware or attacker activities.

B. Trojan: Disguised as legitimate software; does not replicate.

C. Worm: Correct – self-replicating and spreads automatically.

D. Adware: Primarily shows ads; not typically destructive or self-replicating.