What is antivirus? What is major difference between Trojan horse and Worm virus? State.

Antivirus detects, quarantines and removes malware using signature (known patterns) + behaviour (suspicious actions) scanning with daily updates. Must scan pen-drives — main depot infection source. Examples: Windows Defender, Kaspersky.

Basis	Trojan Horse	Worm
Meaning	Hides in useful software, needs user to run	Self-replicates across network without user
Spread	Email attachment, fake installer	LAN/internet scanning, no click needed
Damage	Backdoor, password theft (e.g. fake fuel-bill .exe)	Bandwidth jam, mass infection (e.g. WannaCry)
Prevention	Verify source, block .exe, user training	Patch OS, firewall, segment network

Both need updated antivirus + backup; Trojans need user caution, worms need patching.