Nearly all main border walls today use ________ filtering.

• A. unified threat management
• B. stateful packet inspection
• C. static packet inspection
• D. All of the above

Answer: (B)

Stateful packet inspection is the filtering method most modern border firewalls rely on because it uses context from ongoing connections to decide which packets to allow. By keeping a state table of active sessions and tracking protocol handshakes (like TCP), the firewall can determine whether an incoming packet belongs to a legitimate, established connection or is part of a new, potentially malicious attempt. This context-aware approach is much more effective than examining each packet in isolation, since static, or one-off, inspection cannot tell if a packet fits within an already established session or if it’s trying to misuse a connection. While a border device might include broader security features (the idea of unified threat management), those features describe additional capabilities rather than the filtering method itself. Thus, the best answer is stateful packet inspection, which provides the practical, scalable filtering mechanism used at the network edge.