Explain about various security mechanisms in detail.

Security mechanisms are tools and techniques that protect data and systems and implement the CIA triad — Confidentiality, Integrity, Availability. No single tool is enough; offices use layers together (defence in depth).

1. Identity and Access Control: Ensures only the right person enters and can do only allowed work.

• Authentication: Proves who you are — password, smart card, fingerprint, OTP, multi-factor authentication (MFA). Example: e-attendance with fingerprint + password.
• Authorization: Decides what you can do after login — clerk can enter data but cannot delete; admin can do all. Implemented via user roles and Access Control Lists (ACL).

2. Firewall: A barrier between trusted internal network and untrusted internet. It checks incoming/outgoing packets against rules and blocks suspicious traffic.

• Hardware firewall in router + software firewall in Windows.
• Example: Office firewall blocks Facebook during work but allows email; blocks hacker’s port-scan.

3. IDS and IPS:

• IDS (Intrusion Detection System): Watches and alerts — “attack happening!” like CCTV. Does not block itself.
• IPS (Intrusion Prevention System): Watches and blocks automatically — like security guard. Placed inline in network.
• Together with firewall they form complete perimeter defence.

4. Email Filtering and Anti-spam: Scans emails for spam, phishing links and virus attachments before they reach inbox. Moves junk to spam folder, blocks fake sender domains. Example: “.exe” salary attachment blocked; fake nrb-com-np domain flagged. Offices must also train staff not to click unknown links.

5. Antivirus / Antimalware: Detects, quarantines and removes viruses, worms, Trojans and ransomware.

• Signature-based: Matches known virus patterns — fast but needs daily update.
• Behaviour-based: Watches suspicious behaviour (file encrypting rapidly) to catch new/unknown malware.
• Must auto-update and scan pen-drives — main virus source in Nepal offices.

6. Digital Signature and Encryption:

• Encryption converts readable data to unreadable code during transfer/storage. Only key holder can read. Example: HTTPS, password hashing.
• Digital Signature uses public-key cryptography to prove sender identity and that document was not changed. Legally valid under ETA 2063 in Nepal for e-tender, online forms.

7. Backup and Updates (bonus for full marks): Regular backup (full/incremental) + timely OS/software patching close security holes. 90% attacks exploit old unpatched software.

Conclusion for exam: Write any 5–6 mechanisms with what + how + one office example. End with: layered use of firewall + IDS/IPS + antivirus + MFA + backup gives practical office security.