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Application Links (cont.)
Perimeter Defense (cont.)
- Linux has all three types of firewalls:
- Packet Filtering - Linux can use ipfwadm in the 2.0.x kernel series, and ipchains in the 2.2.x series.
- Stateful Inspection - New in the 2.4.x kernels is a pair of applications called netfilter and iptables. These provide stateful inspection of incoming and outgoing packets. Checkpoint also has a commercial implementation of Firewall-1 for Linux.
- Application proxy - The most common Linux application proxy firewall is Trusted Information Systems' Firewall Toolkit (TIS FWTK). This toolkit comes with an http proxy, a telnet proxy, and so forth. Outbound and incoming packets must pass through the appropriate proxy before passing on.
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