Nmap (“Network Mapper”) is a utility for network discovery and security auditing. It is useful for tasks such as network inventory, managing service upgrade schedules, and monitoring host or service uptime.
Using Nmap you can check the ports and service which are open against that port and information about the operating system installed on the machine. Use the command below from the Linux machine to get such information about the target machine :-
nmap -O hostname or IP address
For Ex-
nmap -O 173.0.142.41
Starting Nmap 5.51 ( http://nmap.org ) at 2013-07-09 20:39 CDT
Nmap scan report for mail5.gohsphere.com (173.0.142.41)
Host is up (0.00042s latency).
Not shown: 990 filtered ports
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PORT STATE SERVICE
25/tcp open smtp
80/tcp open http
110/tcp open pop3
143/tcp open imap
443/tcp open https
465/tcp open smtps
587/tcp open submission
873/tcp closed rsync
993/tcp open imaps
995/tcp open pop3s
——————————–
Device type: general purpose|WAP|firewall|broadband router|webcam
Running (JUST GUESSING): Linux 2.6.X|2.4.X (97%), Linksys Linux 2.4.X (97%), Asus Linux 2.6.X (93%), Check Point Linux 2.4.X (92%), Netgear embedded (89%), AXIS Linux 2.6.X (88%)
Aggressive OS guesses: Linux 2.6.9 – 2.6.21 (97%), OpenWrt White Russian 0.9 (Linux 2.4.30) (97%), OpenWrt 0.9 – 7.09 (Linux 2.4.30 – 2.4.34) (97%), OpenWrt Kamikaze 7.09 (Linux 2.6.22) (97%), Linux 2.6.24 (94%), Asus RT-N16 WAP (Linux 2.6) (93%), Linux 2.6.18 (93%), OpenWrt Kamikaze 7.09 (Linux 2.6.17 – 2.6.21) (93%), Check Point NGX R65 firewall (Linux 2.4.21) (92%), Linux 2.6.20.6 (92%)
No exact OS matches for host (test conditions non-ideal).
OS detection performed. Please report any incorrect results at http://nmap.org/submit/ .
Nmap done: 1 IP address (1 host up) scanned in 7.93 seconds
It really helps to know about the open ports of the server which you’re using or to know about the services you can use on that port and also about the OS installed on the target machine.
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