Which one of the following attacks is MOST effective against an Internet Protocol Security (IPSEC)
based virtual private network (VPN)?

A.
Brute force

B.
Man-in-the-middle

C.
Traffic analysis

D.
Replay

Explanation:
Active attacks find identities by being a man-in-the-middle or by replacing the responder in the
negotiation. The attacker proceeds through the key negotiation with the attackee until the attackee

has revealed its identity. In a well-designed system, the negotiation will fail after the attackee has
revealed its identity because the attacker cannot spoof the identity of the originally-intended
system. The attackee might then suspect that there was an attack because the other side failed
before it gave its identity. Therefore, an active attack cannot be persistent because it would prevent
all legitimate access to the desired IPsec system. http://msgs.securepoint.com/cgi-bin/get/ipsec-
0201/18.html Not C: Traffic analysis is a good attack but not the most effective as it is passive in
nature, while Man in the middle is active.