What is the name of the evasion technique that employs overlapping TCP sequence numbers in small fragments to bypass reassembly checks?

• A. Fragmentation
• B. IDS evasion
• C. ASCII shellcodes
• D. Pre-Connection SYN

Answer: (B)

This question is about evading detection by manipulating how traffic is reassembled. Attackers craft small fragments with overlapping TCP sequence numbers so that when an IDS reassembles the stream to inspect the payload, the result can differ from what the actual target reassembles. This mismatch can cause the IDS to miss malicious content or misinterpret the data, allowing the payload to slip past detection. Because the focus is on dodging IDS checks, this is an IDS evasion technique. Fragmentation describes the general act of breaking data into pieces, but the key here is using that fragmentation specifically to defeat reassembly-based detection. The other options don’t fit: ASCII shellcodes relate to payload encoding, and Pre-Connection SYN pertains to handshake techniques.