Why is monitoring ARP activity important for network security?

• A. To log user activity
• B. To update firmware
• C. To detect potential ARP spoofing or poisoning attacks
• D. To block all traffic

Answer: (C)

Monitoring ARP activity focuses on watching for changes in IP-to-MAC mappings and unusual ARP traffic patterns. Since ARP has no built-in authentication, an attacker can send forged ARP replies to misrepresent a host’s MAC address, creating a man-in-the-middle or causing traffic to be misrouted. By monitoring, you can spot signs like a sudden change in the MAC address tied to an IP, multiple MACs for a single IP, or unsolicited ARP replies, and respond quickly. This enables defenses such as static ARP entries for critical devices, Dynamic ARP Inspection and DHCP snooping on switches, and isolating offending devices to prevent credential theft or traffic interception. Other options don’t address ARP-level security: logging user activity isn’t about ARP integrity, updating firmware is general maintenance, and blocking all traffic would be disruptive and not a targeted security measure.