ICMP (Internet Control Message Protocol), per RFC 792, handles diagnostics (e.g., ping) and errors in IP networks. It’s exploitable in:
A. Ping of Death:
Method: Sends oversized ICMP Echo Request packets (>65,535 bytes) via fragmentation. Reassembly overflows buffers, crashing older systems (e.g., Windows 95).
Fix: Modern OSes cap packet size (e.g., ping -s 65500).
B. Smurf Attack:
Method: Spoofs ICMP Echo Requests to a network’s broadcast address (e.g., 192.168.255.255). All hosts reply, flooding the victim.
Amplification: 100 hosts = 100x traffic.
C. ICMP Flooding:
Method: Overwhelms a target with ICMP Echo Requests (e.g., ping -f), consuming bandwidth/CPU.
Variant: BlackNurse attack targets firewalls.
Technical Details:
ICMP Type 8 (Echo Request), Type 0 (Echo Reply) are key.
Mitigation: Rate-limit ICMP, disable broadcasts (e.g., no ip directed-broadcast).
Security Implications:ICMP attacks are DoS vectors. CNSP likely teaches filtering (e.g., iptables -p icmp -j DROP) balanced with diagnostics need.
Why other options are incorrect:
A, B, C individually:All are ICMP-based; D is comprehensive.
Real-World Context:Smurf attacks peaked in the 1990s; modern routers block them by default.References:CNSP Official Study Guide (Network Attacks); RFC 792 (ICMP).
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