Resource inaccessibility refers to the inability of users to access network services or files that are typically available. This might indicate some form of attack or system failure that is preventing access. For example, a successful Distributed Denial-of-Service (DDoS) attack could inundate the service with traffic rendering it inaccessible. Hardware failures or misconfigurations could also cause a similar issue, but given the context of a security incident, the unavailability due to an attack is the prime concern.