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Verifying Linux Server Security: What Every Admin Needs to Know - Port Scanning
Port scanning, or the process of evaluating ports on a server to identify vulnerabilities, is one method that administrators should employ when looking to evaluate the overall security of a Linux server. Running a port scan on a server reveals which ports are open and receiving information, as well as the security devices that exist between the sender and the target, and can be used to identify potential weak points that could be exploited by attackers. There are an array of excellent port scanners - or applications designed to probe a server or host for open ports - available to Linux users. In this section, we’ll introduce our three favorite open-source port scanners, and direct you to some helpful tutorials demonstrating how to perform a port scan on your Linux servers.
Let’s take a look at three great port scanners available to Linux users:
Nmap, which stands for “Network Mapper”, is by far the most popular and versatile port scanner available - and for good reason. The free and open-source port scanner offers an array of options for performing quick, effective scans on both local and remote networks. Nmap can be used for active port scanning to discover open ports on specific networks/hosts, as well as for host discovery to identify potential hosts that are responding to network requests. Nmap’s capabilities extend beyond port scanning - it can also be used for penetration testing, fingerprinting operating systems and vulnerability scanning, as well as for OS detection and application version detection. Nmap has both CLI and GUI interfaces (the GUI called Zenmap is pictured to the right), and can also be run from the classic command line terminal.
You can learn how to install Nmap on your system download.
Learn how to scan for open ports in Linux with Nmap in this Linuxize tutorial
Unicornscan is the second most popular open-source port scanner (after Nmap). It features renowned asynchronous TCP and UDP scanning capabilities, as well as non-common network discovery patterns that provide alternative ways to find out important details about remote operating systems and services. Unicornscan can be used for both active and passive remote OS, application and component identification. The fast, comprehensive port scanner offers custom module support, customized data-set views and PCAP file logging and filtering.
Learn how to perform multiple types of scans with Unicornscan in this LinuxHint tutorial.
Angry IP Scanner
Thanks to its multi-thread approach which separates each scan, Angry IP Scanner is known for its impressive scanning speed. The free multi platform scaner searches for open ports on any remote network, and then exports scan results into either TXT, XML or CSV files. Other notable features of Angry IP Scanner include its web server & NetBIOS information detection capabilities and its easy, seamless plugin integration with Java.
Angry IP Scanner for Linux can be downloaded linux.
Learn how to use Angry IP Scanner in this TechWiser tutorial.