WoO Day 1 : Introduction

Today marks the first day of the Week of OSSEC. What is OSSEC you ask? Well, I’m glad you asked. Allow me to explain.

According to the OSSEC home page, OSSEC is :

OSSEC is an Open Source Host-based Intrusion Detection System. It performs log analysis, file integrity checking, policy monitoring, rootkit detection, real-time alerting and active response.

It runs on most operating systems, including Linux, MacOS, Solaris, HP-UX, AIX and Windows.

But you have an IDS already, right? One of those big fancy all-in-one units that protects your network, has tons of signatures, and spits out endless reams of data. Or maybe you’re on the Open Source track and you’re using Snort combined with some fancy OSS front end for reporting.

Well, OSSEC is a bit different. It’s a HIDS, not an IDS. In short, this means that OSSEC is designed to monitor a single host and react to events occurring on that host. While this doesn’t sound very useful from the outset, I assure you that this is significantly more useful than you think.

For instance, let’s look at a typical brute-force attack. Your average IDS will allow the traffic through the network as perfectly valid traffic. There is nothing unusual happening at a network layer, so the IDS is content with passing the traffic as normal. Once it hits the server, however, the attack makes itself clear, trying to brute force its way into the server. You can ignore this and hope your password policies are strong enough to cope, but if an attacker is persistent enough, they may eventually worm their way in. Another way to deal with this is through session throttling via the server’s firewall. OSSEC deals with this by identifying the attack and blocking the attacker’s IP.

Sure, fail2ban and other packages offer similar capabilities, but can they also be used to monitor file integrity? How about rootkit detection? Can you centralize their capabilities, using a single host to push out configurations to remote systems? Can they be used in an agentless configuration where a host is monitored without having to install software on it?

OSSEC is extremely powerful and is gaining more capabilities over time. It is in active development with no signs of slowing. In fact, version 2.5 was just released on September 27th.

Over the next week I’ll be explaining some of OSSEC’s capabilities. Ultimately, I suggest you install it on a development system and start poking at it yourself. You can also join the OSSEC mailing list and join in the various on-going conversations.


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