A network administrator need to install a border device on the network that will help ensure FTP commands are not being sent in traffic communicating on port 25.
Which of the following devices will allow for deep packet inspection?

A.
Layer 7 firewall

B.
Web proxy

C.
Layer 3 switch

D.
Protocol analyzer

Explanation:
http://www.infosectoday.com/Articles/Deep_Packet_Inspection_Technologies.htm