Outline
nmap is a network exploration and security scanner, system administrators and individuals can use this software to scan large networks, access to that host is running and what services and other information. nmap supports a number of scanning techniques such as: UDP, TCP connect (), TCP SYN (half open scanning), ftp proxy (bounce attack), reverse signs, ICMP, FIN, ACK scanning, Christmas tree (Xmas Tree), SYN scan and null scan. Details can be obtained from a scan type. nmap also provides several advanced features, such as: the TCP / IP protocol stack feature detection type of operating system, secret scanning, dynamic delay and retransmission calculations, parallel scanning, by scanning the probe close parallel ping a host, scanning the bait, avoid open port filtering detection, direct RPC scan (without port mapping), fragmentation scanning, and flexible target and port settings.
In order to improve the performance of nmap in non-root state, designer of the software put in a lot of effort. Unfortunately, some kernel interfaces (such as raw socket) is required in the root. So it should be possible to use nmap in the root.
nmap run normally get scanned host port list. nmap always gives the well known service name port information (if possible), port number, and protocol state. Status of each port are: open, filtered, unfiltered. open state means that the target host can use this port accept () system call to accept connections. filtered state said: firewall, packet filtering and other network security software to cover this port to prohibit nmap whether to open their probe. unfiltered represents: This port is closed and no firewall / packet filters to detect an attempt to isolate the nmap. Under normal circumstances, the state port basic state are unfiltered, and only under the most ports to be scanned in a filtered status, the port will be displayed in the unfiltered state.
According to options used, nmap may also report the following characteristics of the remote host: operating system used, TCP sequence, the user name is bound to run the application on each port, DNS name, whether the host address is the address spoofing, and some other things.
grammar
nmap [Scan Type(s)] [Options]