Certified Ethical Hacker (CEH) Practice Question

Packet injection after a three-way handshake works only when devices on the path will forward spoofed segments that appear to belong to an existing flow. An IDS/IPS (or a modern stateful firewall) that performs full TCP stream reassembly and validates sequence numbers rebuilds the entire conversation in memory, discards overlapping or out-of-window segments, and flags duplicate/abnormal sequence patterns. Because the malicious fragments will not fit correctly into the reassembled stream, they are dropped or trigger an alert, stopping the hijack attempt despite fragmentation or TTL manipulation. Raising a default TTL, disabling routing, or segregating hosts with static VLANs does not in itself validate sequence numbers or defeat packet injection attacks.