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Multi-layer security strategy

Short answer

A multi-layer security strategy uses independent protective layers (people, physical, perimeter, network, host, application, data, identity, payment) so failure of one layer doesn't compromise the system. For e-commerce, it applies layers from secured data centre and firewalls to encrypted customer data, PCI-DSS compliance, two-factor authentication, and staff training, reducing risk by forcing attackers to defeat multiple controls.

What is a multi layer security strategy? Discuss how multi layer security strategy can be applied to protect e-commerce systems.

A multi-layer security strategy (defence in depth) uses several independent layers of protection so that if one layer fails, the others still protect the system. No single control is trusted alone.

 Policy, training (people)
   Physical security
     Perimeter: firewall, IDS
       Network: VPN, segmentation
         Host: antivirus, patches
           Application: input checks
             Data: encryption, backup

Applying it to an e-commerce system

  1. Physical layer - secured data centre, access control, CCTV, UPS.
  2. Perimeter layer - firewall and DMZ for the web server, IDS/IPS, DDoS protection.
  3. Network layer - HTTPS/SSL/TLS, VPN for admin access, network segmentation (web, application and database servers on separate segments).
  4. Host layer - hardened operating systems, antivirus, regular patches.
  5. Application layer - input validation against SQL injection and XSS, secure session handling, web application firewall, secure coding.
  6. Data layer - encrypted customer and card data, tokenization of card numbers, PCI-DSS compliance, regular backups.
  7. Identity layer - strong passwords, OTP/two-factor login, role-based access for staff, digital certificates.
  8. Payment layer - trusted gateway, 3-D Secure.
  9. Human/procedural layer - security policy, staff training, monitoring logs, audits, incident response plan.

Benefit: an attacker must defeat many layers, risk is reduced and failures are contained.

✓ Answer checked by Claude Opus 5.5 (high effort)

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