Mitigating DoubleDirect Attacks

The man-in-the-middle (MitM) attack intercepts a communication between two systems. Using different techniques, the attacker splits the original TCP connection into 2 new connections, one between the victim and the attacker and the other between the attacker and the server.

A man-in-the-middle technique called DoubleDirect surfaced recently. The technique utilized ICMP redirect packets to create new connections between the victim and the attacker. Since most of GNU/Linux and Windows desktop operating system do not accept ICMP redirect packets, these systems are not affected. However, Android, iOS and OS X accepts ICMP redirect packets hence they are prone to this attack.

The technique allows the attacker to perform eavesdropping if the original TCP connection is unencrypted. For an encrypted TCP connection, such as HTTPS, the eavesdropping is more difficult (unless the CA's private key were compromised by the attacker.)

To prevent DoubleDirect attacks, Dell SonicWALL suggests customers to enable prevention for the following signature:

• IPS sid:5198 "ICMP -- Redirect (5)"