Commands using netstat

Affiche des infos detaillees sur vos connexions reseaux.

Port en ?coute, protocole, paquets, adresses, ustilisateur, PID etc...

Ok so it's rellay useless line and I sorry for that, furthermore that's nothing optimized at all...

At the beginning I didn't managed by using netstat -p to print out which process was handling that open port 4444, I realize at the end I was not root and security restrictions applied ;p

It's nevertheless a (good ?) way to see how ps(tree) works, as it acts exactly the same way by reading in /proc

So for a specific port, this line returns the calling command line of every thread that handle the associated socket

Written for linux, the real example is how to produce ascii text graphs based on a numeric value (anything where uniq -c is useful is a good candidate).

Here is a command line to run on your server if you think your server is under attack. It prints our a list of open connections to your server and sorts them by amount.

BSD Version:

Some commands (such as netcat) have a port option but how can you know which ports are unused?

From 'man netstat'

"netstat -i | -I interface [-abdnt] [-f address_family] [-M core] [-N system]

Show the state of all network interfaces or a single interface

which have been auto-configured (interfaces statically configured

into a system, but not located at boot time are not shown). An

asterisk (``*'') after an interface name indicates that the

interface is ``down''. If -a is also present, multicast

addresses currently in use are shown for each Ethernet interface

and for each IP interface address. Multicast addresses are shown

on separate lines following the interface address with which they

are associated. If -b is also present, show the number of bytes

in and out. If -d is also present, show the number of dropped

packets. If -t is also present, show the contents of watchdog

timers."

Ever logged into a *nix box and needed to know which webserver is running and where all the current access_log files are? Run this one liner to find out. Works for Apache or Lighttpd as long as CustomLog name is somewhat standard. HINT: works great as input into for loop, like this:

Very useful for triage on unfamiliar servers!

Useful to check DDoS attacks on servers.

-p PID and name of the program

-u on a UDP port.

-t also TCP ports

-o networking timer

-n numeric IP addresses (don't resolve them)

-a all sockets

This command does a tally of concurrent active connections from single IPs and prints out those IPs that have the most active concurrent connections. VERY useful in determining the source of a DoS or DDoS attack.

This will tell you who has the most Apache connections by IP (replace IPHERE with the actual IP you wish to check). Or if you wish, remove | grep -c IPHERE for the full list.

List top 20 IP from which TCP connection is in SYN_RECV state.

Useful on web servers to detect a syn flood attack.

Replace SYN_ with ESTA to find established connections

The PID will only be printed if you're holding a root equivalent ID.

usefull in case of abuser/DoS attacks.

-p Tell me the name of the program and it's PID

-l that is listening

-u on a UDP port.

-n Give me numeric IP addresses (don't resolve them)

-t oh, also TCP ports