how to block connections running on non-default ports

[Niranjan S Patil <niranjan.patil () gmail com>]

Hi list,

I recently noticed that our corporate IDS could not block some of
connections that are seemingly unauthorised.

I launched a telnet connection to a remote server on Internet on port
23 and it was successfully blocked by our firewall. I change the
listening port of the telnet server to 443 and launched another telnet
connection on port 443. Neither our firewall or IDS was able to block
this connection.

Aren't IDS supposed to block such masqueraded connections, i.e.,
protocols with non-default ports.

I have less knowledge on IDS, but isn't it simple for them to check
packet headers and block/filter if they are not on right
protocol/port?

Is this normal with all IDS? 

Any help is appreciated.

-- 
Regards,
Niranjan S Patil