Voice over IP systems are more and more replacing Public Switched Telephone Network infrastructures. The number of voice telephony installations and the number of Session Initiation Protocol users is constantly increasing. Attacks against Voice over IP systems are becoming more imaginative and many attacks can cause financial damage, e.g., attackers gain money or create costs for the victim. Therefore, the dependency on available and secure Voice over IP systems to conduct secure business is given. We provide an environment to uncover real-world toll fraud attacks by collecting data using a Voice over IP honeynet solution.