更细节的知识请看nmap的manpage,这里主要是解释nmap的一个GTK前端Zenmap中的默认几个扫描命令的选项:
  intense scan:
  nmap -T4 -A -v
  -T<0-5>: Set timing template (higher is faster)
  -A: Enable OS detection, version detection, script scanning, and traceroute
  -v: Increase verbosity level (use -vv or more for greater effect)
  intense scan plus udp:
  nmap -sS -sU -T4 -A -v
  -sS/sT/sA/sW/sM: TCP SYN/Connect()/ACK/Window/Maimon scans
  -sU: UDP Scan
  -sN/sF/sX: TCP Null, FIN, and Xmas scans
  Intense scan, all TCP ports:
  nmap -p 1-65535 -T4 -A -v
  -p <port ranges>: Only scan specified ports
  Ex: -p22; -p1-65535; -p U:53,111,137,T:21-25,80,139,8080,S:9
  Intense scan, no ping:
  nmap -T4 -A -v -Pn
  -Pn: Treat all hosts as online -- skip host discovery
  Ping scan:
  nmap -sn 192.168.1.0/24
  -sn: Ping Scan - disable port scan
  注:这个用来检测一个子网内有多少机器是在线的
  Quick scan:
  nmap -T4 -F
  -F: Fast mode - Scan fewer ports than the default scan
  注:一般默认nmap会扫描常用的1000个端口,当使用-F后变成常用的100个端口
  Quick scan plus:
  nmap -sV -T4 -O -F --version-light
  -sV: Probe open ports to determine service/version info
  -O: Enable OS detection
  --version-light: Limit to most likely probes (intensity 2)
  注:probe:探针 intensity:强度
  --version-intensity <level>: Set from 0 (light) to 9 (try all probes)