Wireshark
Wireshark for Linux
Installing Wireshark on Linux can be a little different depending on the Linux distribution. If you aren’t running one of the following distros, please double-check the commands.
Ubuntu
From a terminal prompt, run these commands:
sudo apt-get install wiresharksudo dpkg-reconfigure wireshark-commonsudo adduser $USER wireshark
Those commands download the package, update the package, and add user privileges to run Wireshark.
Red Hat Fedora
From a terminal prompt, run these commands:
sudo dnf install wireshark-qtsudo usermod -a -G wireshark username
The first command installs the GUI and CLI version of Wireshark, and the second adds permissions to use Wireshark.
Kali Linux
Wireshark is probably already installed! It’s part of the basic package. Check your menu to verify. It’s under the menu option “Sniffing & Spoofing.”
Data Packets on Wireshark
Now that we have Wireshark installed let’s go over how to enable the Wireshark packet sniffer and then analyze the network traffic.
Capturing Data Packets on Wireshark
When you open Wireshark, you see a screen that shows you a list of all of the network connections you can monitor. You also have a capture filter field, so you only capture the network traffic you want to see.
You can select one or more of the network interfaces using “shift left-click.” Once you have the network interface selected, you can start the capture, and there are several ways to do that.
Click the first button on the toolbar, titled “Start Capturing Packets.”
You can select the menu item Capture -> Start.
Or you could use the keystroke Control – E.
During the capture, Wireshark will show you the packets that it captures in real-time.
Once you have captured all the packets you need, you use the same buttons or menu options to stop the capture.
Best practice says that you should stop Wireshark packet capture before you do analysis.
Analyzing Data Packets on Wireshark
Wireshark shows you three different panes for inspecting packet data. The Packet List, the top pane, is a list of all the packets in the capture. When you click on a packet, the other two panes change to show you the details about the selected packet. You can also tell if the packet is part of a conversation. Here are some details about each column in the top pane:
- No.: This is the number order of the packet that got captured. The bracket indicates that this packet is part of a conversation.
- Time: This column shows you how long after you started the capture that this packet got captured. You can change this value in the Settings menu if you need something different displayed.
- Source: This is the address of the system that sent the packet.
- Destination: This is the address of the destination of that packet.
- Protocol: This is the type of packet, for example, TCP, DNS, DHCPv6, or ARP.
- Length: This column shows you the length of the packet in bytes.
- Info: This column shows you more information about the packet contents, and will vary depending on what kind of packet it is.
Packet Details, the middle pane, shows you as much readable information about the packet as possible, depending on what kind of packet it is. You can right-click and create filters based on the highlighted text in this field.
The bottom pane, Packet Bytes, displays the packet exactly as it got captured in hexadecimal.
When you are looking at a packet that is part of a conversation, you can right-click the packet and select Follow to see only the packets that are part of that conversation.
Wireshark Filters
One of the best features of Wireshark is the Wireshark Capture Filters and Wireshark Display Filters. Filters allow you to view the capture the way you need to see it so you can troubleshoot the issues at hand. Here are several filters to get you started.
Wireshark Capture Filters
Capture filters limit the captured packets by the filter. Meaning if the packets don’t match the filter, Wireshark won’t save them. Here are some examples of capture filters:
host IP-address: this filter limits the capture to traffic to and from the IP address
net 192.168.0.0/24: this filter captures all traffic on the subnet.
dst host IP-address: capture packets sent to the specified host.
port 53: capture traffic on port 53 only.
port not 53 and not arp: capture all traffic except DNS and ARP traffic
Wireshark Display Filters
Wireshark Display Filters change the view of the capture during analysis. After you have stopped the packet capture, you use display filters to narrow down the packets in the Packet List so you can troubleshoot your issue.
The most useful (in my experience) display filter is:
ip.src==IP-address and ip.dst==IP-address
This filter shows you packets from one computer (ip.src) to another (ip.dst). You can also use ip.addr to show you packets to and from that IP. Here are some others:
tcp.port eq 25: This filter will show you all traffic on port 25, which is usually SMTP traffic.
icmp: This filter will show you only ICMP traffic in the capture, most likely they are pings.
ip.addr != IP_address: This filter shows you all traffic except the traffic to or from the specified computer.
Analysts even build filters to detect specific attacks, like this filter to detect the Sasser worm:
ls_ads.opnum==0x09
Additional Wireshark Features
Beyond the capture and filtering, there are several other features in Wireshark that can make your life better.
Wireshark Colorization Options
You can setup Wireshark so it colors your packets in the Packet List according to the display filter, which allows you to emphasize the packets you want to highlight. Check out some examples here.
Wireshark Promiscuous Mode
By default, Wireshark only captures packets going to and from the computer where it runs. By checking the box to run Wireshark in Promiscuous Mode in the Capture Settings, you can capture most of the traffic on the LAN.
Wireshark Command Line
Wireshark does provide a Command Line Interface (CLI) if you operate a system without a GUI. Best practice would be to use the CLI to capture and save a log so you can review the log with the GUI.
Wireshark Commands
- wireshark : run Wireshark in GUI mode
- wireshark –h : show available command line parameters for Wireshark
- wireshark –a duration:300 –i eth1 –w wireshark. : capture traffic on the Ethernet interface 1 for 5 minutes. –a means automatically stop the capture, -i specifics which interface to capture
Metrics and Statistics
Under the Statistics menu item, you will find a plethora of options to show details about your capture.
Capture File Properties:
Wireshark I/O Graph:
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