Which technique is most likely used to evade detection by an Intrusion Detection System (IDS)?

CEH v13 explains that packet fragmentation is a classic and effective IDS evasion technique. By breaking malicious payloads into smaller fragments, attackers attempt to prevent the IDS from reconstructing the full packet stream correctly, thereby avoiding signature detection.

Many IDS systems rely on packet reassembly and pattern matching. Fragmented packets can confuse or overload the reassembly process, especially if the IDS is poorly configured. CEH v13 specifically lists fragmentation, overlapping fragments, and out-of-order packets as evasion techniques used to bypass network defenses.

Option B describes malware propagation, not IDS evasion. Option C is a social engineering attack, unrelated to IDS detection. Option D is a denial-of-service attempt, not a stealth evasion method.

CEH v13 highlights that defending against fragmentation-based evasion requires proper normalization and reassembly configuration in IDS/IPS systems. Therefore, Option A is the correct answer.