Nmap (“Network Mapper”) is an open source tool for network exploration and security auditing.The zenmap project died or didn't make newer packages available. It was designed to rapidly scan large networks, although it works fine against single hosts. Nmap uses raw IP packets in novel ways to determine what hosts are available on the network, what services (application name and version) those hosts are offering, what operating systems (and OS versions) they are running, what type of packet filters/firewalls are in use, and dozens of other characteristics.
#Ubuntu install zenmap upgrade
While Nmap is commonly used for security audits, many systems and network administrators find it useful for routine tasks such as network inventory, managing service upgrade schedules, and monitoring host or service uptime. Key among that information is the “interesting ports table”. That table lists the port number and protocol, service name, and state.
The state is either open, filtered, closed, or unfiltered. Open means that an application on the target machine is listening for connections/packets on that port. Filtered means that a firewall, filter, or other network obstacle is blocking the port so that Nmap cannot tell whether it is open or closed. Closed ports have no application listening on them, though they could open up at any time. Ports are classified as unfiltered when they are responsive to Nmap's probes, but Nmap cannot determine whether they are open or closed. Nmap reports the state combinations open|filtered and closed|filtered when it cannot determine which of the two states describe a port.
#Ubuntu install zenmap software
The port table may also include software version details when version detection has been requested.
Install Nmap on Ubuntu16.04 VM and sudo apt-get install nmap -version Port Scanning Basics When an IP protocol scan is requested (-sO), Nmap provides information on supported IP protocols rather than listening ports. While Nmap has grown in functionality over the years, it began as an efficient port scanner, and that remains its core function. The simple command nmap scans 1,000 TCP ports on the host. While many port scanners have traditionally lumped all ports into the open or closed states, Nmap is much more granular. It divides ports into six states: open, closed, filtered, unfiltered, open|filtered, or closed|filtered. These states are not intrinsic properties of the port itself, but describe how Nmap sees them. For example, an Nmap scan from the same network as the target may show port 135/tcp as open, while a scan at the same time with the same options from across the Internet might show that port as filtered.Īn application is actively accepting TCP connections, UDP datagrams or SCTP associations on this port.
Finding these is often the primary goal of port scanning. Security-minded people know that each open port is an avenue for attack. Attackers and pen-testers want to exploit the open ports, while administrators try to close or protect them with firewalls without thwarting legitimate users. Open ports are also interesting for non-security scans because they show services available for use on the network.Ī closed port is accessible (it receives and responds to Nmap probe packets), but there is no application listening on it. They can be helpful in showing that a host is up on an IP address (host discovery, or ping scanning), and as part of OS detection.
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