Photo by Compare Fibre on Unsplash
The open ports in your hardware could be critical points of vulnerability if the services exposed to them are misconfigured or unpatched. Unfortunately, many organizations are exposing their sensitive resources through such malicious connections, heightening the risk of ransomware attacks, supply chain attacks, and data breaches. Fortunately, free tools can detect all of the open ports in your ecosystem to assess the level of criticality of each exposure.
In this post, we discuss the two best free open port scanners you can start using today to check for open ports in your ecosystem.
What is Open Port Scanning?
Port scanning is the process of analyzing the security of all ports in a network. It involves identifying open ports and sending data packets to select ports on a host to identify any vulnerabilities in received data. Network reconnaissance should be completed regularly to identify and remediate vulnerabilities before cyber attackers discover them. Unfortunately, cybercriminals also use port scanners to garnish vulnerability intelligence about a potential victim before launching a cyberattack.
Because many of these tools are freely accessible, you must assume that cybercriminals are using them to study your open ports. So they cannot be the only security controls protecting your network. This is why network administrators should only use free open port scanners to determine the level of network visibility available to potential cyber attackers. In addition, all free port scanners should be supported with additional security solutions for maximum security. TCP Port scanners can also help penetration testers determine which specific ports accept data to protect them from compromise.
List of Common Network Port Numbers
Every port in a network transports a specific type of network traffic. Each of these ports is assigned a particular number to be easily differentiated.
There are two types of network ports:
TCP – Transmission Control Protocol
UDP – User Diagram Protocol.
What’s the difference between UDP and TCP?
The TCP uses a handshake protocol. TCP also checks each data packet for errors. UDP doesn’t include verification, error checking, or any handshakes. Because of the different processes, TCP is a slower protocol than UDP.
Port numbers range from 0 – 65,535, forming a total of 65,536 ports. These ports are either TCP, UDP, or a combination of both. Because of this extensive range, port numbers are ranked by relevance to shorten the list of network options.
Ports 0-1023 are primarily designed for internet connections.Ports 1024-49151 are ‘registered ports’ designated for exclusive use by registered software corporations and applications. Ports 49152-65,536 are private ports that can be used by anyone.
Tools
1. Nmap
Nmap (short for Network Mapper) is one of the most popular free, open-source port scanning tools. It offers many different port scanning techniques, including TCP half-open scans.
Key features:
Multiple port scanning techniques.
Identifies all open ports on targeted servers.
Operating system detection.
Discovers network services
Scans remote ports
TCP SYN Scanning
UDP and TCP port scanning.
Can scan comprehensive networks housing tens of thousands of network devices. Supports Mac, Linux, Windows Solaris, OpenBSD, Free BSD, and more.
2. Wireshark
Wireshark is a free network sniffing tool used to detect malicious activity in network traffic. This tool can also be used to detect open ports.
Key features:
Reveals request and reply streams in each port.
Malicious network discovery.
Troubleshoots high bandwidth usage.
Offers multiple data packet filters.
Allows users to follow and monitor data streams of interest.
