Which of the following are the countermeasures against a man-in-the-middle attack? Each correct answer represents a complete solution. Choose all that apply.

Question

Options

• AUsing Off-channel verification.
• BUsing Secret keys for authentication.
• CUsing basic authentication.
• DUsing public key infrastructure authentication.

• A
  89% (39)
• C
  11% (5)

Explanation

A man-in-the-middle (MITM) attack occurs when an attacker secretly intercepts and potentially alters communications between two parties who each believe they are communicating directly with the other. Effective countermeasures include: (A) Off-channel verification - confirming session details through a completely separate communication channel (e.g., a phone call to verify a public key fingerprint) makes it extremely difficult for an attacker to intercept both channels simultaneously. (B) Secret keys for authentication - shared secret keys (e.g., HMAC-based message authentication) allow both parties to verify message integrity and source authenticity, detecting any tampering by an interceptor. (D) Public Key Infrastructure (PKI) authentication - digital certificates issued by a trusted Certificate Authority bind a public key to a verified identity, allowing parties to detect forged or substituted keys that a MITM attacker would need to use. (C) Basic authentication is NOT a countermeasure - it encodes credentials in Base64 (essentially plaintext) and is highly vulnerable to interception, making it a liability rather than a defense in MITM scenarios.

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