The hack.lu team and CIRCL announce the new hackathon.lu 2025 event. This 2-day physical Hackathon, held in Luxembourg on April 8th and 9th, 2025, focuses on the development of free and open-source software for cybersecurity. We aim to convene diverse developer groups to collaborate on complex programming challenges within key cybersecurity areas, such as information sharing, threat intelligence, network and system forensics, data mining, network and computer exploitation, and defense techniques. The hackathon’s objectives include improving existing open-source security projects, enhancing interoperability and integration between different security tools, and driving the creation of innovative new solutions.