5 of the Best Free Linux Port Scanners
A port scanner is a utility which probes a server or host to
verify if the virtual ports of a system are open or closed. Ports allow
different applications on the same computer to share
network resources simultaneously.
Computers that are connected to a local area network or
internet run many different services that listen at well-known (and not
so well-known) port numbers. Port numbers range from 0 to 65535, with
port numbers from 0 to 1023 considered to be the well-known
ports. These include ports reserved for the File Transfer Protocol
(FTP), Secure Shell (SSH), telnet, Domain Name System (DNS), Hypertext
Transfer Protocol (HTTP) used in the World Wide Web, Network News
Transfer Protocol (NNTP), to name a few. Port numbers from 1024 to
49151 are known as registered ports, and the range from 49152 to
65535 are allocated to dynamic or private ports.
Port scanning is a popular technique used by attackers to find services
that they may be able to compromise. A port scan assists the attacker
in finding which ports are available. The scan sends a message
to each port, with the response indicating whether the port is used and
can therefore be probed further for weaknesses. There are a variety of
different forms of scanning which include TCP, SYN, UDP, ACK, Window,
and FIN scanning.
However, port scanning has many legitimate uses such as network
inventory and the verification of the security of a network. Port
scanners therefore represent an important tool for users and system
administrators to verify the security policies of their computers and
network.
Linux has a good range of port scanners that help
administrators identify and rectify weaknesses in a system. To provide
an insight into the software that is available, we have compiled a list
of 5 of our favorite port scanners. Hopefully,
there will be something of interest here for administrators or users
that want to scan computers and services that are running on a network.
We give our strongest recommendation to
Nmap, an indispensable utility to gather information about remote
computers.
So, let's explore the 5 port scanners at hand.
For each application we have compiled its own portal page, a full
description with an in-depth analysis of its features, screenshots,
together with links to relevant resources and reviews.
| Port Scanners |
| Nmap |
The Network Mapper |
| Unicornscan |
User-land
Distributed TCP/IP stack |
| Zenmap |
The Network Mapper Front End |
| nast |
Network
Analyzer Sniffer Tool |
| Knocker |
TCP security port scanner |
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Last Updated Sunday, February 05 2012 @ 11:36 AM EST
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