Tag Archives: nfsim

AoIS Interviews Michael Rash, Part 3

Michael Rash HeadshotThe Art of Information Security continues our interview with Michael Rash, Network Security expert and the driving force behind several open source security tools including PSADFWSnort, and FWKnop.

In Part 2 of the interview Michael discussed how network threats, and network counter measures have been evolving. He also touched on the development of his book. Here goes the final installment in this series…

Erik: What would be your recommendations for folks who are adopting Linux (either enthusiasts or corporations) in terms of properly protecting their hosts and networks from network attacks?

Michael: I think that deploying host and network firewalls is a great first step here, and iptables functions admirably. Many people in corporate environments are concerned about the questions of performance, manageability, scalability, and support, and iptables together with some third party software have decent answers to these concerns. For example, the fwbuilder project provides good graphical support for the display and manipulation of iptables policies, and large Linux distributions such as Red Hat and SuSE offer commercial support.

Beyond having proper firewalls deployed, intrusion detection systems are a critical piece to point the way to attempted (and sometimes successful) compromises. Also, strong security mechanisms such as SELinux can provide a powerful barrier to attempted malicious usages of hosts. Finally, patch early and patch often.

Erik:  Do you have any tool or reference recommendations for debugging IP tables firewalls?

Michael: For debugging iptables policies and maintaining tight controls on the type of packets that are allowed to traverse those policies, one of the best techniques is to use tcpdump either on the end points or on the firewall itself (and these may be the same system) and watch how network traffic is allowed to progress. For example, a SYN packet to a port that is filtered will not respond either with a SYN/ACK or a RST, and seeing this behavior with tcpdump is quite easy. At the same time, understanding where in an iptables policy packets are getting dropped (or otherwise messed with) is usually made clear by watching how packet and byte counters are incremented on particular iptables rules. Use ‘iptables -v -n -L’ for this, and couple this with the ‘watch’ command to see how things change. Beyond this, if you have a kernel compiled with support for the iptables TRACE target, then you can use an iptables TRACE rule that causes all packets hitting this rule to be logged. Lastly, for really advanced debugging of iptables code itself, the nfsim project provides a simulator for running Netfilter code within userspace (and hence the ability to test code before running it within the kernel itself where a bug can have dire consequences). The nfsim project can be found here:


Erik: So, you obviously are deeply connected to all things Network IDS/IPS. What kinds of trends have you seen in 2008? Were there any new attack styles that surprised you? Do you have any ideas about what 2009 may hold?

Michael: Well, 2008 will certainly go down in history as the year that people were forced to really pay attention to DNS by the Kaminsky attack. One thing Dan did really well is make it clear just how important DNS is for literally everything on the Internet, and how a flaw there has implications that are difficult to over estimate. Online banking, acquiring SSL certificates, SMTP, “forgot my password links”, and countless other infrastructures depend on DNS information being correct. But, then there were also serious issues in 2008 with BGP and with SSL, so if there was any trend in 2008 I would say that it was the year of security flaws in big Internet infrastructures. In 2009, it will be interesting to see whether this trend remains true for as-yet undiscovered vulnerabilities in other important systems.

Erik: Has your support for open source helped you professionally?

Michael: Absolutely. My current position as a Security Architect on the Dragon IDS/IPS developed by Enterasys Networks is a role that my open source work helped me to acquire. Many forward looking innovations are created by the open source community, and understanding this community helps to guide many companies and the products they develop. Companies are recognizing the power of open source software more and more, and this translates to better professional positions for open source developers and technology enthusiasts.

Many Thanks to Michael !

Thanks a ton for the time and energy you put into this, the first of what I hope will be many, interviews with notables from around the Information Security community.

Thanks, Erik