I'm currently studying scanning techniques and information gathering in a pen testing course, and I have some few questions, you might be asking yourself why this noob "me " isn't asking those questions to the leaders or the staff of that course he joined!!.. lets just say BECAUSE THIS FORUM ROCKS!!
moving on am actually trying to be more comfortable with scanning techniques before moving to the next level when it comes to pen testing,my questions are basic and could sound stupid, well what to say I'm just a beginner.
So I've connected two computers which I own to my LAN, started to scan host B, using host A, tool used:NMAP, few ports showed up after scanning host B, even tho my firewall is on, on host B.
The ports showed up are the most common ports, like FTP, SSH, HTTP...etc
Now I know what is the difference between open/close ports;
-close port means that the port is accessible, and it reacts with the packets sent threw the bus using host A, but the service on that port is not listening.
-open port simply means that the service on that port is currently listening, port is accessible
my question regarding the above topics:
1- when a port return open on the scanning tool, and knowing that the port is listening, does that means that the port is not protected by a firewall? Normally after scanning a port, with the result of "filtered" we could guess that there is a firewall behind it to protect it, so if the port is open does that mean that is it unsecured? and that it could be accessed easily? leading to high risks attacks!
2- what is the difference between a port listening to a service, and a port not listening to a service? I'll give you an example to simplify my question, I happen to own a website, I use FTP to transfer all my files from my PC to the website and vice-verse, I scanned my website IP just to study how the ports react, the FTP port 21 always appear to be "open port", i though that if i only connect to my website threw FTP then the port 21 will be open because at that time it is listening to the service "FTP", and once I disconnect the session between me and the website the port will appear as "close port", but the facts shows that the port 21 is always open on my web??!! Before you say "GOOGLE THAT YOU NOOB", I already did that, and would also like to hear some clarification from experts in this forum "which i respect a lot".
sorry if my questions were kinda messy.