A layer-4 firewall (a device that can look at all protocol headers up to the
transport layer) CANNOT
(A) block entire HTTP traffic during 9:00PM and 5:00AM
(B) block all ICMP traffic
(C) stop incoming traffic from a specific IP address but allow outgoing traffic to
the same IP address
(D) block TCP traffic from a specific user on a multi-user system during 9:00PM
and 5:00AM

• Option A: HTTP is in the application layer.Firewall is at layer 4, it cannot block HTTP data.
  ref from http://www.geeksforgeeks.org/computer-networks-set-3/
• 8 years agoHelpfull: Yes(0) No(0)