\babel@toc {portuguese}{}\relax \contentsline {section}{\numberline {1}Introduction}{2}{}% \contentsline {section}{\numberline {2}Firewall}{2}{}% \contentsline {subsection}{\numberline {2.1}Packet fileter with NAT}{2}{}% \contentsline {subsection}{\numberline {2.2}Packet filtering without NAT}{2}{}% \contentsline {subsection}{\numberline {2.3}External Network}{2}{}% \contentsline {subsection}{\numberline {2.4}Internal Network}{2}{}% \contentsline {section}{\numberline {3}Intrusion Detection}{2}{}% \contentsline {section}{\numberline {4}Conclusion}{2}{}%