List The Open Ports And The Process That Owns Them
netstat -lptu
netstat command to find open ports
# netstat --listen
Display open ports and established TCP connections:
# netstat -vatn
For UDP port try following command:
# netstat -vaun
If you want to see FQDN, remove -n flag:
# netstat -vat
Display list of open ports
# lsof -i
To display all open files, use:
# lsof
To display all open IPv4 network files in use by the process whose PID is 111, use:
# lsof -i 4 -a -p 111
Get Detailed Information About Particular IP address using netstat
This is useful to find out if your server is under attack or not. You can also list abusive IP address using this method.
# netstat -nat | awk '{print $6}' | sort | uniq -c | sort -n
1 CLOSE_WAIT
1 established)
1 Foreign
3 FIN_WAIT1
3 LAST_ACK
13 ESTABLISHED
17 LISTEN
154 FIN_WAIT2
327 TIME_WAIT
Dig out more information about a specific ip address:
# netstat -nat |grep {IP-address} | awk '{print $6}' | sort | uniq -c | sort -n
2 LAST_ACK
2 LISTEN
4 FIN_WAIT1
14 ESTABLISHED
91 TIME_WAIT
130 FIN_WAIT2Busy server can give out more information:
# netstat -nat |grep 202.54.1.10 | awk '{print $6}' | sort | uniq -c | sort -n
15 CLOSE_WAIT
37 LAST_ACK
64 FIN_WAIT_1
65 FIN_WAIT_2
1251 TIME_WAIT
3597 SYN_SENT
5124 ESTABLISHED
Get List Of All Unique IP Address
To print list of all unique IP address connected to server, enter:
# netstat -nat | awk '{ print $5}' | cut -d: -f1 | sed -e '/^$/d' | uniq
To print total of all unique IP address, enter:
# netstat -nat | awk '{ print $5}' | cut -d: -f1 | sed -e '/^$/d' | uniq | wc -l
449
Find Out If Box is Under DoS Attack or Not
If you think your Linux box is under attack, print out a list of open connections on your box and sorts them by according to IP address
# netstat -atun | awk '{print $5}' | cut -d: -f1 | sed -e '/^$/d' |sort | uniq -c | sort -n
1 10.0.77.52
2 10.1.11.3
4 12.109.42.21
6 12.191.136.3
Display Summary Statistics for Each Protocol
# netstat -s | less
# netstat -t -s | less
# netstat -u -s | less
# netstat -w -s | less
# netstat -s
Display Interface Table
You can easily display dropped and total transmitted packets with netstat for eth0:
# netstat --interfaces eth0
The command for finding if you are under DoS attacks:
# netstat -atun | awk '{print $5}' | sed -n -e '/[0-9]\{1,3\}\.[0-9]\{1,3\}\.[0-9]\{1,3\}\.[0-9]\{1,3\}/p’ | sed -n -e '/ESTABLISHED/p' | sed ’s/::ffff://’ | cut -d: -f1 | sort | uniq -c | sort -n
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