Which technique is MOST effective to bypass signature-based IDS?

The correct answer is B because signature-based IDS detection depends on matching known byte patterns, strings, payload structures, or attack signatures. Polymorphism is highly effective against this model because it changes the appearance of the payload while preserving the same functionality. CEH-aligned material explains that IDSs mainly work by comparing traffic against a signature database, and signature detection only identifies attacks whose signatures exist in that database. It also states that polymorphic shellcodes evade IDS by modifying the attack payload so it no longer matches the default IDS signature. Obfuscation is a broader technique and may include encoding or formatting changes, but polymorphism is more directly aimed at defeating static signatures. Encryption can hide traffic from inspection, but it depends on whether the IDS can decrypt or inspect the session. Port scanning is reconnaissance, not IDS bypass. Therefore, polymorphism is the most precise CEH answer.