PDAs Versus Laptops

The first question that beginners ask before assembling their kit is whether a laptop or a PDA should be used for wireless penetration testing of any kind. Our answer is to use both if you can. The main advantage of PDAs (apart from size) is decreased power consumption, letting you cover a significant territory while surveying the site. The main disadvantage is the limited resources, primarily nonvolatile memory. The CPU horsepower is not that important here as we are not cracking AES. Other disadvantages are the limited amount of security tools available in packages and lack of Compact Flash (CF) 802.11 cards with standard external antenna connectors (we have yet to see one). However, Secure Digital (SD) and CF memory cards are getting larger and cheaper, external connectors can be soldered to the cards, and both Linux and BSD can be successfully installed on major PDA brands. In addition, CF-to-PCMCIA adapters or PCMCIA cradles can be used to employ your favorite PCMCIA card with an MMCX connector. PCMCIA cradles for iPAQs supporting two client cards and an auxiliary built-in battery to compensate for the additional power consumption by the cards are simply great.

When we talk about the use of PDAs in wireless penetration testing, we mainly mean Compaq's iPAQs and Sharp Zaurus. Wireless sniffers for other PDAs do exist; for example, the Airscanner Mobile Sniffer (Windows CE; free for personal use, downloaded from http://airscanner.com/downloads/sniffer/amsniffer.exe), and PocketWarrior (Windows CE; GPL, home page at http://pocketwarrior.sourceforge.net/).

However, if you want more than just network discovery and packet capture, you will need a UNIX-enabled PDA with a collection of specific tools we describe in the following two chapters. Sharp Zaurus comes with the Embeddix Linux preinstalled, with the main install-it-yourself alternative being OpenZaurus based on the Debian Linux distribution. Although iPAQs come with Windows CE by default, Linux distributions like Intimate, Familiar and OpenZaurus can be installed on iPAQs by anyone willing to experiment with open source security tools on a StrongARM platform. In fact, you can buy an iPAQ with Familiar Linux preinstalled from http://www.xtops.de. The common GUI for these distributions offered by Xtops is Open Palmtop Integrated Environment (OPIE). OPIE is similar to Trolltech's Qtopia used by the Embeddix distro on Zaurus. Another Linux PDA GUI alternative is the GPE Palmtop Environment, based on a GTK+ toolkit and running over an X server. Unfortunately, the peculiarities of installing Linux on iPAQs go beyond the wireless hacking book boundaries, even though we might include them in further editions. The best place to look for how-to information and help on this topic is http://www.handhelds.org/. Of note, IBM has produced an experimental 802.11 security testing software for iPAQs running Linux. More about this software suite can be found at http://www.research.ibm.com/gsal/wsa/.

Another possibility is running NetBSD to use the brilliant BSD-airtools suite and Wnet (if ported from OpenBSD 3.2). This requires more effort and knowledge than installing Intimate or Familiar, but isn't the pursuit of knowledge what hacking is really about? To find out more about installing BSD on your beloved PDA, check out the NetBSD mail list at http://handhelds.org/hypermail/netbsd/. If you decide to remain on the Windows CE side, the best idea is to get a copy of AirMagnet, Sniffer Wireless PDA version, or PDAlert. Neither solution is cheap, but that is to be expected from proprietary software.

Although a PDA running Linux or BSD can be turned into a very powerful wireless security auditing tool, the inconvenience of using a small keyboard allied to the price of the full kit (additional nonvolatile memory, PCMCIA cradle/CF 802.11 card, PDA-specific GPS device) and the time-consuming Linux/BSD installation (if not preinstalled) means that all but the most determined should stay away from PDA-only wireless security auditing. An additional issue is finding the 802.11a and now, 802.11g cards for PDAs, which are nearly nonexistent. However, there are YellowJacket and YellowJacket Plus suites for iPAQs designed for evaluating 802.11a WLANs and available from Berkeley Varitronics Systems (http://www.bvsystems.com/). Generally, Berkeley Varitronics produces a large variety of brilliant wireless site survey tools for a selection of protocols, although they come at a hefty price.

We have found a compromise in the "PDA vs. laptop" question: Use the PDA running a tool like Kismet or Wellenreiter and some signal strength monitoring software (e.g., wavemon or Wireless Monitor) for site surveys and rogue access point (or even user) discovery and the laptop loaded with the necessary tools for heavy-duty penetration testing.

As for which laptop to choose, just be sure your pick, as long as it can run Linux or BSD, has two PCMCIA slots and as much battery life as possible. The reasons for two and not one PCMCIA slots are explained when we come to certain man-in-the-middle attacks on WLANs in Chapter 8.