UK-based IP Telephony service VoIPtalk suffered a data breach incident in September 2016.
After the company's personnel discovered suspicious behavior and external web attempts to "exploit vulnerabilities in infrastructure" in the quest for client data, user VoIP and SIP passwords have been compromised.
Mark James, Security Specialist at ESET investigated the incident and asked customers to change their passwords.
Source: https://www.databreaches.net/voiptalk-admits-to-possible-data-breach/
"id": "TEL195816622",
"linkid": "telappliant?original_referer=https%3A%2F%2Fwww.google.com%2F",
"type": "Data Leak",
"date": "09/2016",
"severity": "85",
"impact": "4",
"explanation": "Attack with significant impact with customers data leaks"