FreeBSD® 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. There is a variety of tools you can use that go beyond the functionality of a simple firewall, dynamically blocking suspicious hosts, monitoring for intrusions, and controlling access to individual services on a host-by-host basis. Let's go over a few of these tools.

Using PortSentry

PortSentry, from Psionic Software, is a daemon that monitors all incoming network traffic, listening on all of a list of ...