That's because SIP wasn't originally designed to be secure, which means it's easily hacked. The header includes information about the caller's device, the nature of the call that the caller is requesting, and other details necessary to make the call work.
The receiving device which can be a cell phone or a VoIP phone, or perhaps a Private Branch Exchange or PBX , examines the request, and decides whether it can accommodate it or whether it can only work with a subset. The receiving device then sends a code to the sender to indicate that the call is either accepted or that it's not. Some codes may indicate that the call can't be completed, much like the annoying error you see when a webpage is not at the address you requested.
Unless an encrypted connection is requested, all of this takes place as plain text that may travel across the open internet or your office network. There are even tools readily available that will let you listen in on unencrypted phone calls that use Wi-Fi.
How to configure Secure SiP - TLS with 3CX
When folks hear that an underlying protocol isn't secure, they often give up on it. But you don't have to do that here, because protecting a SIP call is possible.
You'll notice this looks a lot like an email address except for the "SIP" at the beginning. Using such an address will let a SIP connection set up a phone call but it won't be encrypted. The problem with even the secure version of SIP is that the encrypted tunnel exists between devices as they route the call from the beginning to the end of the call but not necessarily while the call is passing through the device.
This has proven to be a boon to law enforcement agencies and intelligence services everywhere because it makes it possible to tap VoIP phone calls that might otherwise be encrypted.
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It's worth noting that it's possible to separately encrypt the contents of a SIP call so that, even if the call is intercepted, the contents can't be easily understood. However, you'll need to test this for business purposes to ensure your VPN provider is giving you enough bandwidth in the tunnel to avoid call degradation. Unfortunately, the SIP information itself can't be encrypted, which means that the SIP information can be used to gain access to the VoIP server or the phone system by hijacking or spoofing a SIP call, but this would require a rather sophisticated and targeted attack.
The VLAN, as is decribed in our story on VoIP security , has the advantage of effectively providing a separate network for voice traffic, which is important for a number of reasons, including security, since you can control access to the VLAN in a variety of ways. Click Admin. Under Telephony , click Trunks. Click the External Trunks tab. Select your trunk. Configure an External SIP trunk with a non-default port. Was this article helpful?
Session Initiation Protocol
This field is for validation purposes and should be left unchanged. The security mechanism for this last hop is determined by the domain of the final destination. The proxy server provides a public certificate and UA1 validates it.
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UA1 and proxy server2 authenticate over TLS.