We Rally 'Round The Sniffer (With A Pocket Full Of Cards)

Ahh, the good ol' days.  The days when USC was beating UCLA by 50 points, AirTran was flying nonstops from LAX to Milwaukee and WiFi sniffing folks only had to carry one USB card for 802.11 protocol analysis.  Those days are gone, my friends.  It's time to update which cards we need for which applications.

December of 2011 was a time yours truly looks back on with fond memories for the reasons cited above.  In the wireless world, the good news was that WildPackets OmniPeek had begun supporting monitor mode capture from Atheros-based 802.11a/b/g/n chipsets, thus allowing one USB adapter to be used for any good WiFi sniffing app.

Things change, and when WLAN infrastructure vendors began selling APs that support three-stream spatial multiplexing (thus rendering high rate data frames un-sniffable to the D-Link DWA-160 802.11a/b/g/n USB adapter), the handwriting was on the wall.  The halcyon days of only needing one USB adapter for wireless protocol analysis were numbered.  For a while most client/station devices continued to use one-stream or two-stream spatial multiplexing, thus keeping my old USB friend relevant.

Today, too many devices use three-stream spatial multiplexing for it to be ignored.  If you try to run a protocol analyzer using an adapter that only supports up to two streams, you may end up with a worthless capture.

We can capture three-stream data if we have a three-stream adapter that is compatible with our Wi-Fi sniffing software, but there's a problem.  No single USB adapter works will every application.  If you want to be ready to use any protocol analyzer, you'll have to carry around a pocket full of capture devices.

It is doubtful that you come to this-a-here blog [DiCaprio-in-Django-Unchained voice] to see me whine about changin' tech-nol-gy (see, with a ludicrous Southern Gentleman accent, I can both add syllables and subtract).  So here, then are the current top options for getting a three-stream wireless data capture into a quality Wi-Fi sniffer:

• WildPackets OmniPeek: Still my favorite Wi-Fi sniffer, and now it has a simple option for capturing 450 Mbps data.  The OmniWiFi adapter is a dual-band 802.11a/b/g/n USB adapter that supports three-stream capture.  
• Fluke AirMagnet WiFi Analyzer: AirMagnet is still great software, but the capture options stink.  You're best bet is a laptop with an Intel 6300 internal Wi-Fi interface.  The problem is that rules out virtual machines (since USB adapters are available in virtual machines, but internal adapters are not) and Apple laptops (which use a Broadcom-based Wi-Fi interface).
• Wireshark for Mac OS X: You can capture using the internal three-stream interface on a MacBook Pro (not MacBook Air) using Wi-Fi Diagnostics and open the captured .pcap file in Wireshark.

And this is even leaving out Wireshark for Linux, which works with the old DWA-160.  I'm unsure if there is a three-stream USB adapter that has monitor mode drivers for Linux Wireshark, but if anyone knows of one leave a comment or email me.

The hard truth is that this re-scattering of capture capabilities is annoying to a person like me, but may not matter as much to a WLAN administrator.  If you're just going to use one WiFi sniffer, then you can just choose the appropriate card option and go with it.