While open ports are necessary for any type of communication over the Internet, they can be risky to your online security. This is why you need an open source port checking tool like Nmap to help determine which ports should be closed. This tool can also give you information about how well your security settings and firewall are working.
In this article, we will show you how to scan all ports using the Nmap program. We will also explain what port scanning is and why it is so useful.
Scan all ports with Nmap
Nmap or Network Mapper is a network tool used to scan services, operating systems, and hosts within a computer network. This program was first developed for Linux, but can now be used on other operating systems, such as Windows, macOS, and BSD. Some of the most important features of Nmap include port scanning, host discovery, version detection, network inventory, TCP or IP stack fingerprinting, etc. Today, we will focus on open port scanning.
Port scanning is a process that allows you to determine which ports within a network are open and which are closed. If a port is open, it is configured to accept packets, which are groups of data sent over computer networks. Simply put, open ports are used to send and receive information. Once you scan all of your ports, you can determine which ones are open and possibly exposing sensitive information on your network.
There are over 65,000 ports and Nmap can help you scan them all. This program offers scanning mechanisms, including discovery, default, aggressive, secure, external, malware, version, dos, exploit, streaming, and more. Depending on the scanning mechanism you choose, you may get different results. For example, using secure scanning will not cause the target to fail to scan all ports. If you want to find vulnerabilities in the system, you must use aggressive scanning.
Nmap allows you to scan all ports, a single port, or a series of ports. There is even a command to scan the 100 most used ports. The Nmap command you will need to scan all ports is “nmap –p– 192.168.0.1”, which scans ports 0 to 65,535.
If you want to scan a single port, the command you need to enter is “nmap -p 22 192.168.1.1”. To scan a variety of ports, you will need to insert the following command into the Nmap window: “nmap -p 1-100 192.168.1.1”. Finally, to scan the 100 most common ports, the corresponding command is “nmap -F 192.168.1.1”.
You may notice that the commands for the 100 most common ports and for all ports are almost identical, the only difference is the initial letter (“F” and “p”). That’s why you need to be careful when pasting the code into the dialog box.
The most basic way to use Nmap to call all ports is to start the program, enter the corresponding command, and wait for the scan to complete. Please note that it will take some time for Nmap to scan all ports, approximately 10 to 15 minutes during the entire scanning process, since this program needs to scan more than 65,000 ports. To run the scan, you need a target. Your target can be an IP address, network range, hostname, etc.
The first step is to download. Nmap. You can find different versions of Nmap for specific operating systems, including Windows, Linux (RPM), macOS, and any other operating system. Please note that to use Nmap for any task, you must have an administrator account. To find all the ports on your network, you first need to know their hostname. This is how you do it:
- Press the “Windows” and “R” keys at the same time. This will launch the “Run” dialog box.
- Get into “
cmd” in the box and click “OK.” - Write “
ipconfig /all” in the command prompt window. - Copy your hostname, found under “Windows IP Settings.”
Now that you have your hostname, you can close this window and open Nmap. Here’s what you should do next:
- Paste the hostname into the “Destination” box.
- Next to “Command”, paste “nmap –p– 192.168.0.1” to scan all ports.
- Click the “Scan” button in the upper right corner of the program.
After the scan is complete, Nmap will return a list of ports that have different states. In addition to open and close, ports can also be filtered, unfiltered, open/filtered, and closed/filtered.
What other types of analysis can Nmap perform?
There are different types of scanning techniques and they can even be combined for a specific task. Some of them can only be done by professionals, as they require root access on Unix systems.
Please note that you can only use one method at a time. There are some exceptions, such as UDP and SCTP scans combined with TCP scans. Nmap uses SYN scanning by default, which is also known as half-open scanning. This type of scan can be used to scan thousands of ports in just seconds. SYN scanning requires the following command “nmap -sT 192.168.1.1”. When the scan is complete, it sends a SYN message to Nmap only.
You also have the option to choose scans via TCP connection, UDP port scanning, and more. Ping scans are also quite common. They are the simplest port scans, taking the form of Internet Control Message Protocol (ICMP) requests. We also have XMAS scans, which are also known as the more “stealthy” port scanning mechanisms, as they are rarely blocked by firewalls.
The most important goal of Nmap and other types of port checkers is to find open ports. As useful as it is, an open port can be seen as an open window. You are always at risk of a cyber attack.
Some of the most common open ports are HTTP (80), Proxy (3128), FTP (21), SSH (22), DNS (53), SMTP (25), DHCP (67, 68), SFTP (115), IMAP (143), LPD (515), rsync (873), etc.
Some might assume that closed ports cannot be accessed, but this is not the case. Nmap probe packets can reach closed ports, but will not respond to them. In other words, if you can send packets to closed ports, they will be ignored.
If a closed port is protected by a firewall, it is called a filtered port. If you send a package to a filtered post, you can reach it. It will simply be blocked by the firewall. Sometimes you may encounter unfiltered ports, which are ports that can be open or closed; Nmap just can’t tell which one it is.
Restore network security and stability with Nmap
Nmap may seem complicated to use at first, but you don’t need to be a professional IT specialist to execute the most basic commands. You can use Nmap to scan all ports, one port, a selection of ports, and the 100 most common ports. If you want to scan all ports, Nmap will tell you which ports are open, which will tell you if they are vulnerable to cyber attacks.