Книга: Iptables Tutorial 1.2.2

Debugging, a necessity

Debugging, a necessity

Debugging is more or less a necessity when it comes to iptables and netfilter and most firewalls in general. The problem with 99% of all firewalls is that in the end there is a human being that decides upon the policies and how the rulesets are created, and I can promise you, it is easy to make a mistake while writing your rulesets. Sometimes, these errors are very hard to see with the naked eye, or to see the holes that they are creating through the firewall. Holes that you don't know of or didn't intend to happen in your scripts can create havoc on your networks, and create an easy entry for your attackers. Most of these holes can be found rather easily with a few good tools.

Other than this, you may write bugs into your scripts in other ways as well, which can create the problem of being unable to login to the firewall. This can also be solved by using a little bit of cleverness before running the scripts at all. Using the full power of both the scripting language as well as the system environment can prove incredibly powerful, which almost all experienced Unix administrators should already have noticed from before, and this is basically all we do when debugging our scripts as well.

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