Enterprise companies are increasingly using Microsoft Lync 2010/2013 (a.k.a Skype for Business 2015) services as call centre, internal communication, cloud communication, and video conference platform. These services are based on the VoIP and instant messaging protocols, and support multiple client types such as Microsoft Office 365, Microsoft Lync, Skype for Business, IP phones, and teleconference devices. Also, the official clients are available for mobile devices (e.g. Windows phone, Android and iOS), desktops (Mac, Linux and Windows), and web applications developed with .NET framework.Although the Microsoft Lync platform has been developed along with the new technologies, it still suffers from old VoIP teleconference and platform issues. Modern VoIP attacks can be used to attack Microsoft Lync environments to obtain unauthorised access to the infrastructure. Open MS Lync front-end and edge servers, insecure federation security design, lack of encryption, insufficient defence for VoIP attacks, and insecure compatibility options may allow attackers to hijack enterprise communications. The enterprise users and employees are also the next generation targets for these attackers. They can attack client soft phones and handsets using the broken communication, invalid protocol options, and malicious messaging content to compromise sensitive business assets. These attacks may lead to privacy violations, legal issues, call/toll fraud, and intelligence collection. Attack vectors and practical threats against the Microsoft Lync ecosystem will be presented with newly published vulnerabilities and Microsoft Lync testing modules of the Viproy VoIP kit developed by the speaker. This will be accompanied by live demonstrations against a test environment. A brief introduction to Microsoft Lync ecosystem Security requirements, design vulnerabilities and priorities Modern threats against commercial Microsoft Lync services Demonstration of new attack vectors against target test platform.