On 31 October 2019, Europol conducted the first law enforcement exercise of this kind (CyLEEx19), simulating a cross-border cyberattack on critical infrastructure. The exercise, which was organised by EC3 and ENISA, brought together 20 cybercrime investigators and cybersecurity experts from the public and private sectors. By means of a faked scenario, participants were asked to test the EU Law Enforcement Emergency Response Protocol (see eucrim news of 13 May 2019) by reacting to, responding to, and collectively deciding on simulated large-scale cyberattacks. The attacks were related to incidents, such as misuse of IT resources, unauthorised access to systems, vulnerability exploitations, Distributed Denial of Service (DDoS), and malware infections.