What are common security threats to computer system? Explain. Discuss also the security mechanism to protect against those threats.

Threats break Confidentiality, Integrity or Availability. Each threat needs a matching safeguard — write them as pairs for full marks.

Common threats:

1. Malware — Virus/worm/Trojan/ransomware/spyware damaging files or stealing data.
2. Phishing — Fake mails/sites stealing passwords and OTPs.
3. Hacking/password attacks — Brute force and unpatched exploits.
4. DoS/DDoS — Flooding servers so citizens cannot access services.
5. Social engineering + insider misuse — Tricked staff, USB data theft.
6. Eavesdropping — Snooping on open Wi-Fi without encryption.

Security mechanisms:

1. MFA and access control — Strong passwords + OTP/biometric; role-based rights (enter vs approve) with logs.
2. Firewall + IDS/IPS — Firewall filters by rules; IDS alerts, IPS blocks intrusions.
3. Antivirus + patching — Signature + behaviour scanning; timely OS/app updates; scan pen-drives.
4. Email filtering + training — Spam/phishing filters, block risky attachments; never share OTP, verify sender.
5. Encryption + digital signature — HTTPS and hashed storage; signed official documents (ETA 2063).
6. Backup + monitoring — Offline full/incremental backups; SoC/CERT monitoring and incident response.

Close: no single tool suffices — offices need layered people + technology + policy defence.