Cybersecurity for Beginners by HOFFMAN HUGO & HOFFMAN HUGO

Author:HOFFMAN, HUGO & HOFFMAN, HUGO
Language: eng
Format: epub
Published: 2020-02-08T16:00:00+00:00

Chapter 12 Scanning with NMAP

You can see the webpage below for nmap, which you can find at nmap.org and you can see that you can download the nmap tool for free right from here.

If you look at the website, it says that “nmap is a free and open source utility for network discovery and security auditing.”

Basically it's a scanning tool. Specifically you can use it as a port scanner to see on your servers what ports are opened to assure that you don't have unnecessary ports opened on servers.

Nmap can do quite a bit more than this, and I do recommend that you take a look at it and play around with it. Once you have downloaded it and it's installed on your computer, it's a very quick process.

Nmap syntax just couldn't be simpler. All you have to type is “nmap” and the IP address of the server that you want to scan. So for example your server is hosted on an IP Address of 192.168.1.150, and you want to scan it for open ports, all you have to do is type in the command; “nmap 192.168.1.150” and hit enter.

IP Addresses starting with 192.168.x.x are private IP addresses, so that's what they generally look like if you're scanning your own network server on your network.

There are a couple of other options too for nmap for example “namp –sS” and “nmap –sT”.

“namp –sS” -> sS stands for SYN Scan, so nmap sends SYN to target, target responds with SYN ACK, then nmap sends RST to target.

“nmap –sT” -> sT stands for TCP connect Scan, so this is used to complete the 3-way handshake. Basically, nmap sends SYN to target, target responds with SYN ACK, then nmap sends ACK to target.

The most common TCP flags are as follows:

SYN -> Establish the connection.

ACK -> Acknowledging the message.

RST -> Indicates Reset, due to and error.

FIN -> Tears down the connection.

You can just run nmap from the command prompt. You can either enter in the website or you can enter in the IP address. Either way, nmap is going to work.

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