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Network Traffic Analysis


Command Description
tcpdump --version Prints the tcpdump and libpcap version strings then exits.
tcpdump -h Prints the help and usage information.
tcpdump -D Prints a list of usable network interfaces from which tcpdump can capture.
tcpdump -i (interface name or #) Executes tcpdump and utilizes the interface specified to capture on.
tcpdump -i (int) -w file.pcap Runs a capture on the specified interface and writes the output to a file.
tcpdump -r file.pcap TCPDump will read the output from a specified file.
tcpdump -r/-w file.pcap -l \\| grep 'string' TCPDump will utilize the capture traffic from a live capture or a file and set stdout as line-buffered. We can then utilize pipe (\
tcpdump -i (int) host (ip) TCPDump will start a capture on the interface specified at (int) and will only capture traffic originating from or destined to the IP address or hostname specified after host.
tcpdump -i (int) port (#) Will filter the capture for anything sourcing from or destined to port (#) and discard the rest.
tcpdump -i (int) proto (#) Will filter the capture for any protocol traffic matching the (#). For example, (6) would filter for any TCP traffic and discard the rest.
tcpdump -i (int) (proto name) Will utilize a protocols common name to filter the traffic captured. TCP/UDP/ICMP as examples.

Tcpdump Common Switches and Filters

Switch/Filter Description
D Will display any interfaces available to capture from.
i Selects an interface to capture from. ex. -i eth0
n Do not resolve hostnames.
nn Do not resolve hostnames or well-known ports.
e Will grab the ethernet header along with upper-layer data.
X Show Contents of packets in hex and ASCII.
XX Same as X, but will also specify ethernet headers. (like using Xe)
v, vv, vvv Increase the verbosity of output shown and saved.
c Grab a specific number of packets, then quit the program.
s Defines how much of a packet to grab.
S change relative sequence numbers in the capture display to absolute sequence numbers. (13248765839 instead of 101)
q Print less protocol information.
r file.pcap Read from a file.
w file.pcap Write into a file
host Host will filter visible traffic to show anything involving the designated host. Bi-directional
src / dest src and dest are modifiers. We can use them to designate a source or destination host or port.
net net will show us any traffic sourcing from or destined to the network designated. It uses / notation.
proto will filter for a specific protocol type. (ether, TCP, UDP, and ICMP as examples)
port port is bi-directional. It will show any traffic with the specified port as the source or destination.
portrange Portrange allows us to specify a range of ports. (0-1024)
less / greater "< >" less and greater can be used to look for a packet or protocol option of a specific size.
and / && and && can be used to concatenate two different filters together. for example, src host AND port.
or or Or allows for a match on either of two conditions. It does not have to meet both. It can be tricky.
not not is a modifier saying anything but x. For example, not UDP.


Command Description
tshark -h Prints the help menu.
tshark -D List available interfaces to capture from.
tshark -i (int) Capture on a selected interface. Replace (int) with the interface name or number.
tshark -i eth0 -f "host (ip)" apply a filter with (-f) looking for a specific host while utilizing tshark
D Will display any interfaces available to capture from and then exit out.
L Will list the Link-layer mediums you can capture from and then exit out. (ethernet as an example)
i choose an interface to capture from. (-i eth0)
f packet filter in libpcap syntax. Used during capture.
c Grab a specific number of packets, then quit the program. Defines a stop condition.
a Defines an autostop condition. It can be after a duration, specific file size, or after a certain number of packets.
r (pcap-file) Read from a file.
W (pcap-file) Write into a file using the pcapng format.
P Will print the packet summary while writing into a file (-W)
x will add Hex and ASCII output into the capture.
h See the help menu


Capture Filter Description
host x.x.x.x Capture only traffic pertaining to a certain host
net x.x.x.x/24 Capture traffic to or from a specific network (using slash notation to specify the mask)
src/dst net x.x.x.x/24 Using src or dst net will only capture traffic sourcing from the specified network or destined to the target network
port # will filter out all traffic except the port you specify
not will capture everything except the variable specified. ex. not port 80
and AND will concatenate your specified ports. ex. host and port 80
portrange x-x Portrange will grab traffic from all ports within the range only
ip / ether / tcp These filters will only grab traffic from specified protocol headers.
broadcast / multicast / unicast Grabs a specific type of traffic. one to one, one to many, or one to all.
Display Filter Description
ip.addr == x.x.x.x Capture only traffic pertaining to a certain host. This is an OR statement.
ip.addr == x.x.x.x/24 Capture traffic pertaining to a specific network. This is an OR statement.
ip.src/dst == x.x.x.x Capture traffic to or from a specific host.
dns / tcp / ftp / arp / ip filter traffic by a specific protocol. There are many more options.
tcp.port == x filter by a specific tcp port.
src.port / dst.port ==x will capture everything except the port specified.
and / or / not AND will concatenate, OR will find either of two options, NOT will exclude your input option. eq # Allows us to follow a tcp session in which we captured the entire stream. Replace (#) with the session to reassemble.
http Will filter for any traffic matching the http protocol.
http && image-jfif This filter will display any packet with a jpeg image file.
ftp Filters for the ftp protocol.
ftp.request.command Will filter for any control commands sent over ftp control channel.
ftp-data Will show any objects transfered over ftp.