VoIP (Voice over IP) systems more and more replacing PSTN (Public Switched Telephone Network) infrastructureswhat increases dependency of available and secure VoIP systems for successful business. Attacks against VoIP systems are becoming more imaginative and many attacks can cause damage, e.g., gain money for attackers or create costs for the victim. Therefore, in this paper the current security status of VoIP systems are described with observations of VoIP attacks in a honeynet. The achieved results can help to adapt existing prevention system to avoid the recognized and analyzed attacks in a productive environment.