SCAPY(1) General Commands Manual SCAPY(1)

scapy - Interactive packet manipulation tool

scapy [options]

This manual page documents briefly the Scapy tool.

Scapy is a powerful interactive packet manipulation tool, packet generator, network scanner, network discovery, packet sniffer, etc. It can for the moment replace hping, parts of nmap, arpspoof, arp-sk, arping, tcpdump, tshark, p0f, ...

Scapy uses the Python interpreter as a command board. That means that you can use directly Python language (assign variables, use loops, define functions, etc.)

The idea is simple. Those kinds of tools do two things : sending packets and receiving answers. That's what Scapy does : you define a set of packets, it sends them, receives answers, matches requests with answers and returns a list of packet couples (request, answer) and a list of unmatched packets. This has the big advantage over tools like nmap or hping that an answer is not reduced to (open/closed/filtered), but is the whole packet.

On top of this can be used to build more high-level functions, for example, one that does traceroutes and give as a result only the start TTL of the request and the source IP of the answer. One that pings a whole network and gives the list of machines answering. One that does a portscan and returns a LaTeX report.

Options for Scapy are:

display usage
header-less mode, also reduces verbosity.
increase log verbosity. Can be used many times.
use PRESTART_FILE instead of $HOME/.config/scapy/prestart.py as pre-startup file
do not run prestart file
use STARTUP_FILE instead of $HOME/.config/scapy/startup.py as startup file
do not run startup file

Only the vital commands to begin are listed here for the moment.

lists supported protocol layers. If a protocol layer is given as parameter, lists its fields and types of fields. If a string is given as parameter, it is used to filter the layers.
lists scapy's main user commands.
this object contains the configuration.

$HOME/.config/scapy/prestart.py This file is run before Scapy core is loaded. Only the conf object is available. This file can be used to configure the CLI, configure parameters such as the conf.load_layers list to choose which layers will be loaded, or change the logging level (for instance):

conf.interactive_shell = "bpython"
log_loading.setLevel(logging.WARNING)
conf.load_layers.remove("bluetooth")
conf.load_layers.append("new_layer")

$HOME/.config/scapy/startup.py This file is run after Scapy is loaded. It can be used to configure more of Scapy behaviors, like un-registering layers:

conf.prog.pdfreader = "xpdf"
split_layers(UDP,DNS)

More verbose examples are available in the documentation at https://scapy.readthedocs.io/. Just run scapy and try the following commands in the interpreter.

Test the robustness of a network stack with invalid packets:

sr(IP(dst="172.16.1.1", ihl=2, options=["verb$2"], version=3)/ICMP(), timeout=2)

Packet sniffing and dissection (with a bpf filter or tshark-like output):

a=sniff(filter="tcp port 110")
a=sniff(prn = lambda x: x.show)

Sniffed packet re-emission:

a=sniff(filter="tcp port 110")
sendp(a)

Pcap file packet re-emission:

sendp(rdpcap("file.cap"))

Manual TCP traceroute:

sr(IP(dst="www.google.com", ttl=(1,30))/TCP(seq=RandInt(), sport=RandShort(), dport=dport)

Protocol scan:

sr(IP(dst="172.16.1.28", proto=(1,254)))

ARP ping:

srp(Ether(dst="ff:ff:ff:ff:ff:ff")/ARP(pdst="172.16.1.1/24"))

ACK scan:

sr(IP(dst="172.16.1.28")/TCP(dport=(1,1024), flags="A"))

Passive OS fingerprinting:

sniff(prn=prnp0f)

Active OS fingerprinting:

nmap_fp("172.16.1.232")

ARP cache poisoning:

sendp(Ether(dst=tmac)/ARP(op="who-has", psrc=victim, pdst=target))

Reporting:

report_ports("192.168.2.34", (20,30))

The official website: https://scapy.net/
The GitHub Development repository: https://github.com/secdev/scapy/
The official documentation: https://scapy.readthedocs.io/en/latest/

Does not give the right source IP for routes that use interface aliases.

May miss packets under heavy load. This is a restriction from python itself

Session saving is limited by Python ability to marshal objects. As a consequence, lambda functions and generators can't be saved, which seriously reduce the usefulness of this feature.

BPF filters don't work on Point-to-point interfaces.

Philippe Biondi and the Scapy community.

March 24, 2024