VoIP Security
Security in VoIP has not been a very popular subject so far, but with the increasing demand for VoIP, it is becoming an important concern. VoIP security threats are increasing in number.
VoIP Security Threats - Making Your VoIP Secure
VoIP Phishing - What It Is And How It Works
Do Softphones Make My Network or Machine More Vulnerable? Using Firewalls

For phone users who want a type of VoIP is more or less as their existing fixed line with traditional phones, the most appropriate types of VoIP services are subscription and equipment services. They are intended mainly to households and small businesses. Upon subscription, the user is sent an adapter (ATA) and is given a phone number. This requires an Internet connection, which adds cost, but the overall cost is relatively much weaker. Added benefits are the many features that come with VoIP.
Factors Affecting VoIP Voice Quality VoIP Drawbacks Running VoIP on a Wireless LAN