nmap命令
是一款开放源代码的网络探测和安全审核工具，是Network Mapper的缩写。其设计目标是快速地扫描大型网络。nmap可以发现网络上有哪些主机，主机提供了什么服务（应用程序名称和版本号），并探测操作系统的类型及版本信息。
如果系统没有nmap命令，则可以使用下面的命令来安装：
nmap [Scan Type] [option] (target specification)
扫描目标可以为IP地址、子网地址等，如192.168.1.2或10.0.0.0/24。
nmap命令的参数选项及说明
-sS TCP同步扫描（TCP SYN）
-ST TCP连接扫描
-sn 不进行端口扫描，只检查主机正在运行。该选项与老版本的-sP相同
-sU 扫描UDP端口
-sV 探测服务版本信息
-Pn 只进行扫描，不ping主机
-PS 使用SYN包对目标主机进行扫描。默认是80端口，也可以指定端口，格式为-PS22或-PS22-25,80,113,1050,35000，记住PS和端口号之间不要有空格
-PU 使用udp ping扫描端口
-O 激活对TCP/IP指纹特征（fingerprinting）的扫描，获得远程主机的标志，也就是操作系统类型
-V 显示扫描过程中的详细信息*
-S<IP> 设置扫描的源IP地址
-g port 设置扫描的源端口
-oN 把扫描的结果重定向到文件中
-iL filename 从文件中读取扫描的目标
-p<端口> 指定要扫描的端口，可以是一个单独的端口，也可以用逗号分隔开多个端口，或者使用“-”表示端口范围
-n 不进行DNS解析，加快扫描速度
-exclude 排除指定主机
-excludefile 排除指定文件中的主机
查看主机当前开放的端口
[root@cs6 ~]# nmap 10.0.0.100
Starting Nmap 5.51 ( http://nmap.org ) at 2019-05-07 16:49 CST
Nmap scan report for 10.0.0.100
Host is up (0.0000040s latency).
Not shown: 998 closed ports
PORT STATE SERVICE
22/tcp open ssh
80/tcp open http
Nmap done: 1 IP address (1 host up) scanned in 6.83 seconds扫描主机的指定端口
[root@cs6 ~]# nmap -p 1024-65535 10.0.0.100
Starting Nmap 5.51 ( http://nmap.org ) at 2019-05-07 17:01 CST
Nmap scan report for 10.0.0.100
Host is up (0.0000040s latency).
All 64512 scanned ports on 10.0.0.100 are closed
Nmap done: 1 IP address (1 host up) scanned in 7.18 seconds扫描局域网内所有的IP
[root@cs6 ~]# nmap 10.0.0.0/24
Starting Nmap 5.51 ( http://nmap.org ) at 2019-05-07 17:02 CST
Nmap scan report for 10.0.0.1
Host is up (0.00023s latency).
Not shown: 999 filtered ports
PORT STATE SERVICE
3306/tcp open mysql
MAC Address: 00:50:56:C0:00:08 (VMware)
Nmap scan report for 10.0.0.2
Host is up (0.00013s latency).
Not shown: 999 closed ports
PORT STATE SERVICE
53/tcp filtered domain
MAC Address: 00:50:56:F4:FB:52 (VMware)
Nmap scan report for 10.0.0.100
Host is up (0.0000040s latency).
Not shown: 998 closed ports
PORT STATE SERVICE
22/tcp open ssh
80/tcp open http
Nmap done: 256 IP addresses (3 hosts up) scanned in 25.94 seconds
[root@cs6 ~]# nmap -sn 10.0.0.0/24 #<==使用-sn选项不扫描端口。
Starting Nmap 5.51 ( http://nmap.org ) at 2019-05-07 17:03 CST
Nmap scan report for 10.0.0.1
Host is up (0.000089s latency).
MAC Address: 00:50:56:C0:00:08 (VMware)
Nmap scan report for 10.0.0.2
Host is up (0.00013s latency).
MAC Address: 00:50:56:F4:FB:52 (VMware)
Nmap scan report for 10.0.0.100
Host is up.
Nmap done: 256 IP addresses (3 hosts up) scanned in 21.05 seconds
[root@cs6 ~]# nmap -sn 10.0.0.1-10 #<=可以使用这种地进范围进行扫描。
Starting Nmap 5.51 ( http://nmap.org ) at 2019-05-07 17:04 CST
Nmap scan report for 10.0.0.1
Host is up (0.000034s latency).
MAC Address: 00:50:56:C0:00:08 (VMware)
Nmap scan report for 10.0.0.2
Host is up (0.00015s latency).
MAC Address: 00:50:56:F4:FB:52 (VMware)
Nmap done: 10 IP addresses (2 hosts up) scanned in 6.77 seconds探测目标主机的服务和操作系统的版本
[root@cs6 ~]# nmap -O -sV 10.0.0.100
Starting Nmap 5.51 ( http://nmap.org ) at 2019-05-07 17:05 CST
Nmap scan report for 10.0.0.100
Host is up (0.000090s latency).
Not shown: 998 closed ports
PORT STATE SERVICE VERSION
22/tcp open ssh OpenSSH 5.3 (protocol 2.0)
80/tcp open http?
1 service unrecognized despite returning data. If you know the service/version, please submit the following fingerprint at http://www.insecure.org/cgi-bin/servicefp-submit.cgi :
SF-Port80-TCP:V=5.51%I=7%D=5/7%Time=5CD14A57%P=x86_64-redhat-linux-gnu%r(N
SF:ULL,1D,"I\x20love\x20linux\x20www\.wenyule\.top\n");
No exact OS matches for host (If you know what OS is running on it, see http://nmap.org/submit/ ).
TCP/IP fingerprint:
OS:SCAN(V=5.51%D=5/7%OT=22%CT=1%CU=35109%PV=Y%DS=0%DC=L%G=Y%TM=5CD14A63%P=x
OS:86_64-redhat-linux-gnu)SEQ(SP=106%GCD=1%ISR=109%TI=Z%CI=Z%II=I%TS=A)OPS(
OS:O1=MFFD7ST11NW7%O2=MFFD7ST11NW7%O3=MFFD7NNT11NW7%O4=MFFD7ST11NW7%O5=MFFD
OS:7ST11NW7%O6=MFFD7ST11)WIN(W1=FFCB%W2=FFCB%W3=FFCB%W4=FFCB%W5=FFCB%W6=FFC
OS:B)ECN(R=Y%DF=Y%T=40%W=FFD7%O=MFFD7NNSNW7%CC=Y%Q=)T1(R=Y%DF=Y%T=40%S=O%A=
OS:S+%F=AS%RD=0%Q=)T2(R=N)T3(R=N)T4(R=Y%DF=Y%T=40%W=0%S=A%A=Z%F=R%O=%RD=0%Q
OS:=)T5(R=Y%DF=Y%T=40%W=0%S=Z%A=S+%F=AR%O=%RD=0%Q=)T6(R=Y%DF=Y%T=40%W=0%S=A
OS:%A=Z%F=R%O=%RD=0%Q=)T7(R=Y%DF=Y%T=40%W=0%S=Z%A=S+%F=AR%O=%RD=0%Q=)U1(R=Y
OS:%DF=N%T=40%IPL=164%UN=0%RIPL=G%RID=G%RIPCK=G%RUCK=G%RUD=G)IE(R=Y%DFI=N%T
OS:=40%CD=S)
#<= -O 显示系统版本，但是nmap命令是根据探测的TCP/IP指纹与自己的指纹库进行对比的。如果不在指纹库之内的系统就会无法识别。
Network Distance: 0 hops
OS and Service detection performed. Please report any incorrect results at http://nmap.org/submit/ .
Nmap done: 1 IP address (1 host up) scanned in 18.61 seconds上面的输出信息中不仅包含了端口号，而且还包括了服务的版本号。在网络安全性要求较高的主机上，最好能够屏蔽服务版本号，以防止黑客利用特定版本的服务漏洞进行攻击。
来源：oschina
链接：https://my.oschina.net/u/4366482/blog/3544110