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Showing posts from April, 2018

Scapy 802.11 Cheat Sheet

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I've been taking a look at Scapy as I've been learning more about Python. It's a great Python-based tool for capturing, analyzing and creating network packets. There are some great resources to learn more bout Scapy, and even some cheat sheets out there.

But, as there were quite a few new concepts (for me) and my own interest is in Scapy for 802.11 related activities, I put together my own Scapy for 802.11 cheat sheet. You can grab a copy from here if it may be useful to you.

References:
Scapy 802.11 cheat sheet Scapy docs: https://scapy.readthedocs.io/en/latest/Building Network Tools With ScapySANS Scapy Cheat Sheet

Randomized MAC addresses in 802.11 Probe Frames

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To address perceived privacy issues, some wireless clients adopt a randomized MAC address in probe frames when probing  for wireless networks. In this post  I take a quick look at how you might see clients using randomized MAC addresses. 
Background When a wireless LAN client needs to find a nearby access point to join a Wi-Fi network, it has two choices:
Passive scanning: a client will listen to beacon frames, broadcast by nearby access points, that advertise networks that it makes available. This can be quite a slow process, as a client cycles though channels and waits to hear beacons.Active scanning: a client will cycle through channels and send out probe frames to proactively query nearby APs for a specific wireless network (SSID). This will generally be a faster method of finding networks that the client is configured to join, and may be used by all clients in conjunction with passive scanning.
One (unfortunate) side-effect of active scanning is that a client advertises its presenc…

Wireshark Capture Filters for 802.11

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Generally, when performing over the air captures of WLAN traffic with Wireshark, the workflow adopted is as follows:

pick a specific channel where target traffic residesswitch the capture adapter to that channelcapture all 802.11 traffic over the air on that channel Once a sample of traffic has been captured, the capture is stopped and analysis of the traffic using Wireshark's built-in display filters can begin.
In most situations, this is the best workflow to adopt. It ensures that all required frames are captured. Filtering wireless traffic while capturing frames is very problematic due to the complexity of 802.11 frame exchanges. It is very easy to miss parts of interactions between stations if you filter traffic as it is being captured.
However, there are a few edge cases where it may be useful to filter over-the-air frames at the point of capture. This will mean that only the filtered frames are available to display in Wireshark - all other frames are lost - but in some rare c…