DescriptionTracking flows within a single device, as well as tracking the full path a flow takes in a network, are core components in securing networks. Malicious traffic can be easily identified and its source blocked. Traditional methods have performance and precision shortcomings, while new programmable devices open up new possibilities. In this paper we present methods based on the P4 programming language that allow to track flows in a device, as well methods toward full path tracking. A core component of this work are Bloom filters, which we have implemented fully in P4. To validate our approach and implementation we have carried a study in a specific use case, namely the detection of SYN attacks.