Networking/Computing Tips/Tricks

As those who have studied our Wireless Profile (available from the Profile Repository) know, there are a number of great display filters used to hunt down issues on Wireless LAN's.  For example, when you see a lot of Disassociations and Deauthentications, there may be trouble brewing within the WLAN.  Perhaps those events are being caused by a malicious source, and not the Access Point.  

On a recent troubleshoot, we wanted to only capture when those events occurred, so instead of using a display filter, we wanted to use a capture filter.

Here is how I solved the problem.  I used T-Shark.

To start, I openned Windows Powershell (I am trying to teach myself to use Powershell more than CMD, but like anyone else who has used Microsoft since before Windows, I struggle!) and with my AirPcap interface plugged in checked to make sure I could see the interface.  You will see below that first I changed directory to the Wireshark program directory (in Powershell you have to put the command in quotes when there is a 'space' in the path), then I ran T-Shark to display the current interfaces (again a Powershell thing, you have to start the command with './' tyo get it to execute):

wlantshark1

We clearly see that it is the first interface in the list.

Now we can issue the following command:

tshark -i 1 -f "subtype deauth or subtype disassoc"

The result (I let it run for a little while, CTRL-C will stop):

wlantshark2

How cool is that??  We can quickly see the MAC addresses involved (they should match systems I am expecting to send these packets, else I have an intruder).

There is so much more you can do with T-Shark using this type of capture filter procedure.  Keep in mind this is Berkeley Packet Filter (BPF) syntax and a good reference for the syntax can be found here.

To see some of our other T-Shark articles - look here.

Let us know what other clever T-Shark uses you come up with.

Comments powered by CComment

Find by Tag

4G Networks 5G Networks 6LoWLAN 6LoWPAN 802.11 802.11ah 802.11ax 802.11ay 802.11az Ad-Hoc Addressing Analysis Ansible Architecture ARP Assessment AToM Automation Baseline BGP Bloom's Taxonomy Cable cat CellStream Cellular Central Office Cheat Sheet Chrome Cisco Cloud CMD Company Policy Computer Consulting Data Center Data Networking Dependencies DHCPv6 DNS Docker Documentation Dublin-Traceroute dumpcap Earth Earthquakes ECMP Ethernet Ethics Etiquette Evaluation Field Operations Fragmentation G-MPLS Gauge GeoIP GNS3 Google GQUIC Hands-On History Home Network ICMP ICMPv6 IEEE 802.11p IEEE 802.15.4 India Internet IoT IPv4 IPv6 IRINN IS-IS L2VPN L3VPN LDP LifeNet Linux LLN LoL M-BGP MAC Macro Microsoft Milky Way mininet Monitoring MPLS mtr MTU Multicast Murphy Name Resolution Netcat NetMon netsh Networking nmap NSE Observations OLPC Online School OpenFlow OSPF OSPFv2 OSPFv3 OSX OTT Paris-Traceroute Parrot PIM PMTU Policy POTS POTS to Pipes PPP Profile Project Management PW3E QoS QUIC Railroad Remote Desktop Requirements Resume Review RIP Routing RPL RSVP Rural SDN Security Service Provider Small Business SONET Speed SSL Status Storms Subnetting SYSCTL T-Shark TCP TCP/IP Telco Telecom 101 Telecommunications Telephone Testing Tools Traceroute Traffic Engineering Training Travel Tunnel Ubuntu Utility Video Virtualbox Virtualization VoIP VRF VXLAN Wi-Fi Wi-Fi 4 Wi-Fi 5 Wi-Fi 6 Windows Wireless Wireless 5G Wireshark WLAN Writing Zenmap ZigBee

Twitter Feed