Internal vs. External Penetration Testing

In the past, I've talked about the merits of penetration testing (a.k.a. pen-testing) and several related tools. One thing I've not covered much is the difference between internal and external pen-testing. Today's Webcast, "Zen and the Art of Maintaining an Internal Penetration Testing Program," by Paul Asadoorian of PaulDotCom (which has a great weekly security podcast) is what started me thinking about the differences between the two.External pen-testing is the traditional, more common approach to pen-testing. It addresses the ability of a remote attacker to get to the internal network. The goal of the pen-test is to access specific servers and crown jewels within the internal network by exploiting externally exposed servers, clients, and people. Whether it's an exploit against a vulnerable Web application or tricking a user into giving you his password over the phone, allowing access to the VPN, the end game is getting from the outside to the inside.

Internal pen-testing takes a different approach -- one that simulates what an insider attack could accomplish. The target is typically the same as external pen-testing, but the major differentiator is the "attacker" either has some sort of authorized access or is starting from a point within the internal network. Insider attacks have the potential of being much more devastating than an external attack because insiders already have the knowledge of what's important within a network and where it's located, something that external attackers don't usually know from the start.

In addition to Paul's Webcast, the other item that put me into an attack mindset was this morning's release of Metasploit Framework 3.2. The latest version includes a slew of new exploits and features for handling packet injection and capture, additions for speeding up exploit development, automatic exploitation of Web browsers using the included client-side attacks, and more. Metasploit is an incredibly full-featured pen-testing tool that should be included in every security professional's toolkit. Definitely take a look at Paul's Webcast; he has a lot of great real-world examples of using tools for conducting an internal pen-test.

John H. Sawyer is a Senior Security Engineer on the IT Security Team at the University of Florida. The views and opinions expressed in this blog are his own and do not represent the views and opinions of the UF IT Security Team or the University of Florida. When John's not fighting flaming, malware-infested machines or performing autopsies on blitzed boxes, he can usually be found hanging with his family, bouncing a baby on one knee and balancing a laptop on the other. Special to Dark Reading.