Terri works for a security consulting firm that is currently performing a penetration test on First National Bank in Tokyo. Terri's duties include bypassing firewalls and switches to gain access to…

Question

Options

• APoison the switch's MAC address table by flooding it with ACK bits
• BCrash the switch with aDoS attack since switches cannot send ACK bits
• CEnable tunneling feature on the switch
• DTrick the switch into thinking it already has a session with Terri's computer

• A
  14% (7)
• B
  2% (1)
• C
  6% (3)
• D
  78% (38)

Explanation

In TCP, a SYN packet initiates a new connection, while an ACK packet is only sent after a session has already been established. Many stateless packet filters and older network devices only block inbound SYN packets (new connections) but permit inbound ACK packets (assuming they belong to an existing outbound session). By sending a packet with the ACK bit set, Terri tricks the switch or stateless firewall into believing a legitimate session already exists between her machine and the target, allowing the packet to pass through access controls that would otherwise drop it. This is an ACK-based firewall bypass / session spoofing technique.

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