Master Port Scanning with Nmap - Page 2

Continued From Page 1

OS identification

Variations in different vendors' TCP/IP stacks mean that it's possible to identify – or have a good stab at identifying – the OS running on each device on the network by analyzing the packets received from them. Nmap can do this for you using its own OS-identification engine if you specify the –O option: nmap –O 192.168.1.5. (See figure 7)

Graphical Front-Ends

If you don't like using command line programs and remembering the various options, the good news is that a number of Nmap front-ends are available, including NmapFE and the more flexible and arguably easier to use UMIT

With UMIT you can enter a target IP range, and choose a preset scan from a drop down box. If none of these suit your needs the Command Wizard allows you to build a scan by clicking boxes in a series of forms. As you choose the various components of your scan an Nmap command is slowly built up so you can see the command line options corresponding to the choices you make.

The custom scans you build using the wizard can be saved for reuse later.

The results are presented both graphically – by host or by service – and in a terminal window within the GUI. (See figure 9)

Port scanning is an important way of getting a handle of what's on your network, and is also a key way for hackers to scout out any vulnerabilities. Nmap is a very important security tool, and the more you pay around with it and explore its features, the more you'll know about you network and the work that needs to be done to secure it.

So do yourself and your organization a favor: download a copy sooner rather than later, and have at it!