15. Conclusion

Firewall technologies provide more or less thorough traffic filtering, depending on their capabilities in terms of functionality and performance. Filtering equipment includes filtering routers that perform basic filtering on IP and TCP/UDP headers with high performance. They also include proxies specialized in application protocol filtering with a very wide choice of protocols and applications, as well as boxes combining the filtering functions of filtering routers, stateful packet inspection, proxies and other security functions such as IDS/IPS, VPN and antivirus.

Today's challenges are threefold:

• the quality of filtering, which must take into account more and more content without compromising filtering performance;

• responsiveness to the development of new attacks and viruses;...