Cisco BroadWorks Device Management (DMS) servers are under continuous attack, as bad actors seek to access SIP Device configuration details. They use ths configurations to compromise the service, committing toll fraud, including traffic pumping costing millions of dollars per year. This article explains defensive approaches and gives a complete configuration to mitigate these attacks using a free, open source tool.
The NIST Cybersecurity Framework is applied to assess and improve security defenses in Civilian government organizations and many enterprises. It can be used as a tool developing your Telecom / VoIP / Voice Fraud defenses.
Thinking of your deployment as "small" can lead to all kinds of unwise security decisions. The idea that you can manually configure things to perfection often leads to production deployments that are unsecured, unmanageable, and subject to cyber attack.