Attackers exploit SMBv1 to spread malware across hosts.

The correct answer is A, Worm-like propagation. In CEH malware-threat concepts, a worm is malware that self-replicates and uses a computer network to send copies of itself to other systems without requiring human action. CEH-related material describes worms as self-replicating malware that use networks to spread to other systems and commonly consume resources while duplicating themselves. The scenario specifically says attackers exploit SMBv1 to spread malware across hosts, which matches worm behavior because the malware moves laterally from one vulnerable machine to another through a network service. This behavior is commonly associated with attacks such as WannaCry, where an SMBv1 vulnerability was weaponized so the malware could scan for vulnerable systems and spread via SMB after infection. Phishing involves tricking users through messages or websites, credential stuffing uses reused username/password pairs, and DoS focuses on denying availability. Since the key behavior is automated spreading across hosts through SMBv1, the best answer is worm-like propagation.