Question
[Ubuntu]: Can't open any port
I followed the following guide:
and tried to open port 80, but I still have nothing open or listening:
netstat -plunt
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name
tcp 0 0 127.0.0.1:3306 0.0.0.0:* LISTEN 1051/mysqld
tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN 965/sshd
tcp6 0 0 :::22
The strangest thing is that I could connect to the server yesterday and today it isn’t working anymore and the only thing I changed was to add a DNS entry on Digital Ocean.
Could this have anything to do with it?
I tried even to disable any protection with the following commands:
$ sudo iptables -X
$ sudo iptables -t nat -F
$ sudo iptables -t nat -X
$ sudo iptables -t mangle -F
$ sudo iptables -t mangle -X
$ sudo iptables -P INPUT ACCEPT
$ sudo iptables -P FORWARD ACCEPT
$ sudo iptables -P OUTPUT ACCEPT
but still only port 22 is accessible. What could be the reason for this?
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Why have a firewall in the first place?
Your running daemons could still get exploited?
Make sure you know what you have running and on what ports. Secure those daemons which would be much better then implementing a firewall to allow traffic only to certain ports which are in essence the only ports that are actually being used anyway!
netstat -pluntwill only list ports that something is actively listening on. Do you have a web server listening on port 80? Is Apache or Nginx installed?