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Securely Exposing FreePBX for Remote Access with a Focus on SIP and RTP Ports (alien.top)

submitted 11 months ago by saygon90@alien.top to c/voip@netheads.online

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Hi, due to a very extensive project, we need to expose FreePBX to the internet. Specifically, we are concerned with the SIP and RTP ports. The purpose of this action is to allow logging into the system using softphones and configured phones without the need for VPN.

In the past, I noticed that exposing port 5060 results in numerous brute force attacks where the attacker tries to impersonate an extension that exists in the system. However, due to the lack of a password, they are unable to make a phone call. Does an attacker, without knowledge of the extension password, have the ability to make calls at the expense of the client?

Ports such as 443, 80, 22, etc., will not be exposed to the world, only the ports required for telephony.

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[–] saygon90@alien.top 1 points 11 months ago (1 children)

My suggestion would be that you should know which extensions are nomadic and setup your configuration such to only allow those to register from outside your network and the non-nomadic ones only from within.

The main challenge with such solutions is the dynamic IPs of clients. Unfortunately, I cannot whitelist clients because they will be logging in from different IPs every day.

Make sure you are using complex passwords and different ones for each extension.

I use passwords that are generated automatically by FreePBX, and these passwords are presumably complex enough.

[–] trekologer@alien.top 1 points 11 months ago

I cannot whitelist clients because they will be logging in from different IPs every day.

That's fine, but you should know which extensions are going to be logging in from different IPs and make your configuration allow those while at the same time restrict for extensions that you know will always be on your local network (ie: hard phones on desks in office). You could also limit those nomadic extensions from making calls to expensive destinations.

I use passwords that are generated automatically by FreePBX, and these passwords are presumably complex enough.

You'd be surprised at home many organizations use the same password for all their extensions. Or maybe you wouldn't be surprised.