Combined 3 Banks — Assistant Programmer Written Exam: 2018প্রশ্ন ও সমাধান

Definition: malware ("malicious software") is any program designed to damage, disrupt, steal from, or gain unauthorized access to a computer system.

Malware	Behaviour
Virus	Attaches to a host program/file and replicates when the host is executed; can corrupt or delete files
Worm	Self-replicates and spreads across a network without needing a host file or user action, consuming bandwidth/resources
Trojan Horse	Disguises itself as legitimate software; does not self-replicate but opens a backdoor or steals data once run
Ransomware	Encrypts the victim's files and demands payment for the decryption key
Spyware	Secretly monitors user activity (keystrokes, browsing) and exfiltrates data without consent

graph TD
  M[Malware] --> V[Virus]
  M --> W[Worm]
  M --> T[Trojan Horse]
  M --> R[Ransomware]
  M --> S[Spyware]

Five countermeasures:

1. Keep OS/applications patched and updated to close known vulnerabilities.
2. Deploy and regularly update antivirus/anti-malware software with real-time scanning.
3. Use a firewall and network segmentation to limit lateral spread (especially against worms).
4. Train users to recognize phishing emails/attachments, the main Trojan/ransomware delivery vector.
5. Maintain regular, offline/immutable backups so ransomware cannot hold data hostage.

Exam takeaway: the key distinguishing test is does it need a host file (virus) vs does it self-propagate over a network (worm) vs does it disguise itself but not replicate (Trojan) — countermeasures pair layered technical controls (patching, AV, firewall) with user-awareness training and backups.