Since the start of the EOSC-Hub project, EGI CSIRT and EUDAT Security have regularly held joint F2F meetings. For our most recent meeting, however, we were glad to also welcome security experts from Open Science Grid (OSG) – this also gave us the opportunity to discuss how we could improve collaboration between the security teams. As a result, besides reports from the various activity leaders in EGI CSIRT, there was a focus on a future Security Service Challenge (SSC), where we plan to challenge the collaboration of the participating teams in an incident response scenario with a red/blue team exercise. As a preparatory step, and to explore how well our existing policies and procedures are aligned, a table top exercise is already scheduled for later this year.