Security-minded people know that each open port is an avenue for attack. Finding these is often the primary goal of port scanning. 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 Six port states recognized by NmapĪn application is actively accepting TCP connections, UDP datagrams or SCTP associations on this port. These states are not intrinsic properties of the port itself, but describe how Nmap sees them. It divides ports into six states: open, closed, filtered, unfiltered, open|filtered, or closed|filtered. While many port scanners have traditionally lumped all ports into the open or closed states, Nmap is much more granular. The simple command nmap scans 1,000 TCP ports on the host. While Nmap has grown in functionality over the years, it began as an efficient port scanner, and that remains its core function. $ nmap -dns-servers ] # (Servers to use for reverse DNS queries) $ nmap -system-dns # (Use system DNS resolver) $ nmap -resolve-all # (Scan each resolved address) $ nmap -R # (DNS resolution for all targets) $ nmap -traceroute # (Trace path to host) $ nmap -disable-arp-ping # (No ARP or ND Ping) An administrator may be comfortable using just an ICMP ping to locate hosts on his internal network, while an external penetration tester may use a diverse set of dozens of probes in an attempt to evade firewall restrictions $ nmap -sL # (List Scan) Network administrators may only be interested in hosts running a certain service, while security auditors may care about every single device with an IP address. Of course what makes a host interesting depends greatly on the scan purposes. Scanning every port of every single IP address is slow and usually unnecessary. One of the very first steps in any network reconnaissance mission is to reduce a (sometimes huge) set of IP ranges into a list of active or interesting hosts.
If you want to get a summary of nmap’s command just run nmap without any command like this: $ nmap Nmap’s power can be summarized as follows: In addition to the classic command-line Nmap executable, the Nmap suite includes an advanced GUI and results viewer (Zenmap), a flexible data transfer, redirection, and debugging tool (Ncat), a utility for comparing scan results (Ndiff), and a packet generation and response analysis tool (Nping).
Nmap runs on all major computer operating systems, and official binary packages are available for Linux, Windows, and Mac OS X. It was designed to rapidly scan large networks, but 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.
Many systems and network administrators also find it useful for tasks such as network inventory, managing service upgrade schedules, and monitoring host or service uptime.
Latest release: version 0.9.13 on (9 years, 4 months ago).Nmap or Network Mapper is a free and open source utility for network discovery and security auditing. It can filter traffic to be shown, and can read traffic from a file as well as live from the network. It supports Ethernet, WLAN, FDDI, Token Ring, ISDN, PPP and SLIP devices. Hosts and links change in size with traffic. 28, 2006 (15 years, 9 months ago).įeaturing link layer, IP, and TCP modes, EtherApe displays network activity graphically with a color coded protocols display.
It currently recognizes TCP, UDP and ICMP across Ethernet, PPP, SLIP, FDDI, Token Ring and null interfaces, and understands bpf filter logic in the same fashion as more common packet sniffing tools, such as tcpdump and snoop. ngrep is a pcap-aware tool that will allow you to specify extended regular or hexadecimal expressions to match against data payloads of packets. Ngrep strives to provide most of GNU grep's common features, applying them to the network layer. It sports a NetFlow/sFlow emitter/collector, an HTTP-based client interface for creating ntop-centric monitoring applications, and RRD for persistently storing traffic statistics. In Web mode, it acts as a Web server, creating an HTML dump of the network status. In interactive mode, it displays the network status on the user's terminal. Ntop shows network usage in a way similar to what top does for processes.