Nmap is Linux command-line tool for network exploration and security auditing. This tool is generally used by hackers and cybersecurity enthusiasts and even by network and system administrators. It is used for the following purposes:
- Real time information of a network
- Detailed information of all the IPs activated on your network
- Number of ports open in a network
- Provide the list of live hosts
- Port, OS and Host scaning
Installing Nmap Command
In case of Debian/Ubuntu
sudo apt-get install nmap
In case of CentOS/RedHat
yum install nmap
Working with Nmap Command
1. To scan a System with Hostname and IP address. First, Scan using Hostname
Now let’s Scan using IP Address
The nmap command allows scanning a system in various ways. In this we are performing a scan using the hostname as “geeksforgeeks” and IP address “22.214.171.124”, to find all open ports, services, and MAC addresses on the system.
2. To scan using “-v” option.
nmap -v www.geeksforgeeks.org
It is used to get more detailed information about remote machine.
3. To scan multile hosts
nmap 126.96.36.199 188.8.131.52 184.108.40.206
We can scan multiple hosts by writing IP addresses or hostnames with nmap.
4. To scan whole subnet
We can scan a whole subnet or IP range with nmap by providing “*” with it. It will scan a whole subnet and give the information about those hosts which are Up in the Network.
5. To scan to detect firewall settings.
sudo nmap -sA 220.127.116.11
Detecting firewall settings can be useful during penetration testing and vulnerability scans. To detect it we use “-sA” option. This will provide you with information about firewall being active on the host. It uses an ACK scan to receive the information.
6. To identify Hostnames
sudo nmap -sL 18.104.22.168
We use “sL” option to find hostnames for the given host by completing a DNS query for each one. In addition to this “-n” command can be used to skip DNS resolution, while the “-R” command can be used to always resolve DNS.
7. To scan from a file
nmap -iL input.txt
If we have a long list of addresses that we need to scan, we can directly import a file through the command line. It will produce a scan for the given IP addresses.
8. To get some help
We use the “-h” option if we have any questions about nmap or any of the given commands. It shows the help section for nmap command, including giving information regarding the available flags.
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