Identify Your Computer Services from Ports and Protocols

You can also determine what programs are running on a system by looking at what ports are
open and what protocols are in use.
Start by looking at your own local computer. Go to a command line or shell prompt and run
the netstat program using the -a (or all) switch:
netstat -a
The computer will display a list of open ports and some of the services that are using those
ports:
Active Connections

Proto       Local Address                             Foreign Address                                 State
TCP        YourComputer:microsoft-ds          YourComputer:0                            LISTENING
TCP        YourComputer:1025                     YourComputer:0                            LISTENING
TCP        YourComputer:1030                     YourComputer:0                            LISTENING
TCP        YourComputer:5000                     YourComputer:0                            LISTENING
TCP        YourComputer:netbios-ssn            YourComputer:0                            LISTENING
TCP        YourComputer: 1110                     216.239.57.147:http                     TIME_WAIT
UDP       YourComputer:microsoft-ds            *:*
UDP       YourComputer:isakmp                    *:*
UDP      YourComputer:1027                        *:*
UDP      YourComputer:1034                        *:*
UDP      YourComputer:1036                        *:*
UDP      YourComputer:ntp                           *:*
UDP      YourComputer:netbios-ns                *:*
UDP      YourComputer:netbios-dgm             *:*

From this you can see many of the programs and services that are running on your local
computer – many of which you don't even realize are running.
Another program, called fport, provides information similar to that which netstat does, but it
also details which programs are using the open ports and protocols. (Fport is available for free
download from www.foundstone.com.)
Another program, called nmap (for network mapper), will more thoroughly probe your
computer for open ports. When nmap is run, it will display a list of open ports and the services
or protocols that use those ports. It may also be able to determine what operating system
your computer is using. For example, if you run nmap on your local computer, you might see
the following output:
Port              State       Service
22/tcp              open     ssh
68/tcp              open     dhcpclient
139/tcp            open     netbios-ssn
445/tcp            open     microsoft-ds
Device type: general purpose
Running: Linux 2.4X|2.5.X
OS details: Linux Kernel 2.4.0 – 2.5.20
Uptime 1.024 days (since Sat Jul 4 12:15:48 2004)
Nmap is available on your Hacker Highschool or L. A. S. cd. It is also available for download
from  insecure



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