During a red team simul-ation, an attacker crafts packets with malformed checksums so the IDS...

CEH v13 outlines insertion attacks as IDS evasion methods in which attackers send packets deliberately crafted so that the IDS processes them differently from the target host. In an insertion attack, malformed packets appear legitimate to the IDS—allowing malicious traffic to blend with benign inspection results—while the end host rejects or modifies the packets due to incorrect checksums, invalid flags, or protocol inconsistencies. As a result, the IDS sees one set of reconstructed data, while the actual host processes a different version or nothing at all. CEH emphasizes that intrusion detection systems may not follow full TCP/IP stack validation, making them susceptible to deception by malformed or borderline-conformant packets. Polymorphic shellcode (Option B) changes payload signatures, not packet structure. Session splicing (Option C) splits payload across packets to evade pattern matching but does not rely on checksum manipulation. Fragmentation attacks (Option D) divide traffic into smaller fragments, not alter validity fields. The described behavior fits insertion attacks precisely.