Tracing the source and path of traffic flows is an important problem that is useful in different network security and forensic solutions. Many solutions have been proposed for IP traceback in the past few decades, based on logging or marking, or a combination. Yet, there is no ubiquitously deployed traceback solution in the Internet. While scalability is the challenge facing logging-based approaches, marking-based approaches reveal sensitive information of ISP networks. In this work, we look into the problem of preserving the privacy of ISP networks in marking-based traceback solution. To this end, we propose the first privacy-preserving solution for IP traceback, that does not reveal the topological information of ISP networks, while still serves traceback queries. We present both numerical analysis and simulation-based studies, to evaluate the performance of our solution.