Wireshark

Wireshark是一個免費開源的網路封包分析軟體。網路封包分析軟體的功能是截取網路封包，並盡可能顯示出最為詳細的網路封包資料。在GNU通用公眾授權條款的保障範圍底下，使用者可以以免費的代價取得軟體與其程式碼，並擁有針對其原始碼修改及客製化的權利。

實用技巧
Learning
tcpdump

實用技巧

通用語法

條件語法：

==
!=
>
<
>=
<=
in

邏輯語法：

&&  # AND
||      # OR
!       # NOT

常用篩選：

type: host, port
dir: src, dst
proto: tcp, udp, ftp, http

SIP 相關

tcpdump

timeout 6m tcpdump -i eth0 host <sip-trunk-ip> -n -s 0 -vvvv  -w carrier.pcap

Wireshark

更多與 sip 有關的 filter 語法：https://www.wireshark.org/docs/dfref/s/sip.html

只顯示 REGISTER 行，Filter: sip.CSeq.method == REGISTER

其他

遠端監聽指令

ssh root@192.168.0.1 tcpdump -n -i any -w- 'not \( port 22 and host 192.168.0.1 \)' |etherape -r-

Filter 速查表

For Cybersecurity

Learning

tcpdump

List the interfaces

sudo tcpdump -D

Capture All traffic

tcpdump -i eth0
tcpdump -i wlan0

To a File

tcpdump -i eth0 -w capture.pcap
tcpdump -i any -w capture.pcap -nn 'ip and port 80'

# Set Timeout
timeout 6m tcpdump -i eth0 -w capture.pcap

Read a file (.pcap)

-nn: Disable port and protocol name lookup.
-r : Read capture data from the named file.
-v : Display detailed packet data.
-X : Display the hexadecimal and ASCII output format packet data. Security analysts can analyze hexadecimal and ASCII output to detect patterns or anomalies during malware analysis or forensic analysis.

tcpdump -r capture.pcap
tcpdump -r capture.pcap -nn -v 'ip and (port 80 or port 443)'
tcpdump -nn -r capture.pcap -X

Filter

# Filter by Source IP
tcpdump src 192.168.0.1

# Filter by Destination IP
tcpdump dst 192.168.0.1

# Filter by Port
tcpdump port 80

# Filter by Protocol
tcpdump icmp

# Protocol and Port
tcpdump tcp port 443

# Source and Destination
tcpdump src 192.168.0.1 and dst 192.168.0.2

tcpdump -i any -w capture.pcap -n 'ip and port 80'

Display in ASCII

# Dispaly in ASCII
tcpdump -A

# Display in Hexadecimal
tcpdump -X

Specific Number of Packets

tcpdump -c 100

Display

# Capture and Display IPv6 Traffic
tcpdump -6

# Capture and Display Traffic in Timestamp Format
tcpdump -tttt

SSH Connections

# -l: real-time
# -e: including ethernet headers
tcpdump -i eth0 'tcp port 22' -l -e

HTTP Request and Response

tcpdump -i eth0 -s 0 -A -n 'tcp dst port 80'

IP Range and Protocol

tcpdump -i eth0 'net 192.168.0.0/24 and (tcp port 22 or icmp)'

DNS Traffic

tcpdump -i eth0 'udp port 53' -nnvvv

FTP Traffic

tcpdump -i eth0 -s 0 'tcp port 21'

遭受 DDos 攻擊時自動擷取封包

interface=ens1
dumpdir=/home/user/automatic-tcp-dump/
while /bin/true; do
  pkt_old=`grep $interface: /proc/net/dev | cut -d :  -f2 | awk '{ print $2 }'`
  sleep 1
  pkt_new=`grep $interface: /proc/net/dev | cut -d :  -f2 | awk '{ print $2 }'`
  pkt=$(( $pkt_new - $pkt_old ))
  echo -ne "\r$pkt packets/s\033[0K"
  if [ $pkt -gt 30000 ]; then
    echo -e "\n`date` Under Attack. Capturing Packets..."
    sudo  tcpdump -n -i $interface -s0 -c 20000 -w $dumpdir/dump.`date +"%Y%m%d-%H%M%S"`.pcap
    echo "`date` Packets Captured."
    sleep 300  && pkill -HUP -f /usr/sbin/tcpdump
  else
    sleep 1
  fi
done

Cheat Sheets

$tcpdump_commands.jpg$