Explain the concept of defense in depth with an example

• A. A Single Firewall Suffices
• B. Multiple Layers Of Controls (Perimeter Firewall, Network Segmentation, Endpoint Protection, MFA, Encryption) So One Failure Doesn’t Break Security
• C. Only Rely On User Training
• D. Only Rely On Antivirus

Answer: (B)

Defense in depth means protecting a system with multiple, independent security controls so that if one layer is breached, others still stand between attackers and the assets. For example, a company can combine a perimeter firewall to block unsolicited traffic, network segmentation to limit how far an intruder can move inside the network, endpoint protection on devices to detect and block malware, multi-factor authentication to prevent account compromise even with stolen credentials, and encryption to make data unreadable if it’s accessed or exfiltrated. Together, these layers ensure that a single failure doesn’t lead to a full breach: credentials might be stolen, but MFA can stop access; a firewall alone can be bypassed, but segmentation and endpoint defenses reduce damage; even if data is taken, encryption protects its confidentiality. Relying on just one control—like a single firewall, training alone, or antivirus—is insufficient because threats exploit gaps in any single layer.