When I run a nmap scan against a remote target, it shows port 25 closed but an online nmap tool like (https://hackertarget.com/nmap-online-port-scanner/) shows that port 25 is open.
sudo nmap -sS -v 18.104.22.168 -p 25 --reason PORT STATE SERVICE REASON 25/tcp closed smtp reset
Which result is true and why the other one is displaying a different result?
PORT STATE SERVICE REASON 25/tcp closed smtp reset TRACEROUTE (using port 80/tcp) HOP RTT ADDRESS 1 61.28 ms 192.168.0.1 2 4.16 ms rsm4151x-ndr.net.hrz.tu-darmstadt.de (22.214.171.124) 3 14.89 ms corel506-rsm4151x.net.hrz.tu-darmstadt.de (126.96.36.199) 4 4.19 ms cores101-corel506.net.hrz.tu-darmstadt.de (188.8.131.52) 5 4.18 ms mx01-1.mpi-bremen.de (184.108.40.206)
I ran with traceroute option of nmap. How to find where is the firewall or IDS or even it's existing or not ?