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The first tool in any hackers toolkit is almost always a port scanner. For those who don’t know what a port scanner is, it is a program that looks at which ports are open or closed on lots of computers, really quickly. An open port means that there is some program running on that port on the other computer. What makes NMap special is that it will tell you not only what port is open, but what program is running, what version the program is, and what operating system the computer is running. You can also get loads on other information, like what brand of computer it is. Additionally, NMap can recognize printers, routers etc from how they behave.

How is the useful to a hacker? Well, If you know the program and version number then is possible to exploit security failures in that program. Look up some exploits on metasploit or milw0rm. There is a large avalibity of code that can be used if you know exactly what your attacking.

Go download nmap, and then learn how to use it. Some useful command lines:

  • T#.  this command sets the speed of the scan. Replace the # with a number from 1-5. Higher numbers means faster results, but slower scans will be more accurate.
  • -sV. This tells the program to search for version numbers. You can set the intensity from 1-9 with –version-intensity #.
  • -F. This tells the NMap to limit it’s searches to common ports, like 80, 21, 553 etc. This will make the scan faster, but could easily miss something running on an unusual port.
  • -v. Verbose. This means that NMap will output more information about what it is doing. You can use it twice to get lots of information.
  • -A. Scan for everything. This will automatically scan for operating system information, versions, open ports, netbios infomation, everything.

One Comment

  1. Nice post, man. The man page for nmap is way to confusing.

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