Always permit SSH from the internal network to the firewall. The goal is to build policy rules to do the following: 1. In the following example I use this idea to add firewall policy rules dynamically to block SSH scanners. Such an empty rule set can be very useful if you populate it with rules using some external script after firewall policy has been loaded. If it is left empty, it won't make packet checks and return back to the top level rule that called it right away. It is not required however that you put any rules in this branch rule set. Using branch rule set with external script that adds rules "on the fly" to prevent ssh scanning attacks Branch rule sets created in the Firewall Builder GUI get translated into user-defined chains (iptables) or anchors (pf) in the generated configuration. File nf :įirewall Builder Cookbook 357 # Tables: (1) table /fw2-pf-rate_nf || exit 1 Rules from the file "fw2-pf-rate_nf" are loaded into anchor "rate_limit". When configuration with multiple rule sets is compiled for PF, each new branch rule set has its own separate file with the name composed from the name of the firewall object and the name of the rule set object. The generated PF config is split so that main policy rules are in the file "nf" and rules for the rule set "rate_limit" are in the file "fw2-pf-rate_nf". Rate-Limiting Rule for PF I am using the same three rules in the main policy to rate-limit connections to the firewall itself and two servers behind it. First, we'll need to change rate limiting parameters because its implementation in PF is different from that in iptables. Let's try to recompile the same rules for PF.
Unfortu- nately, branching can not be implemented in Cisco IOS access lists and PIX. In iptables it is user-defined chains, in PF it is anchors. An action that creates a branch is available in Firewall Builder only if the target firewall platform provides some kind of mechanism to support it.
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