FreeBSD6 Unleashed

Preventing Intrusions and Compromises

Firewalls, password policies, and encryption go a long way toward protecting your system from malicious access. They still aren’t enough, though, to defend against a really determined hacker who has a “rootkit” or other tool designed to take advantage of some known weakness in one of your system’s services.

You can use a variety of third-party tools in FreeBSD that go beyond the functionality of a simple firewall to dynamically block suspicious hosts, monitor for intrusions, and control access to individual services on a host-by-host basis. The following sections describe a few of these tools.

Using PortSentry

PortSentry, from Psionic Software, is a daemon that monitors all incoming network traffic to detect ...