System security is one of the most important duties of an administrator. Ensure that your system is protected by setting up proper policies for users and groups, and hardening your systems (especially servers) when exposed to attack from the Internet. Firewall tools are useful in blocking attacks, and intrusion detection should be used to discover any system anomalies as early as possible.
We've now been through pretty much all of the major administrative areas of Debian Linux, not counting individual software suites. Next, we will cover some advanced administration techniques.
