An alert triggered by exceeding network bandwidth usage is a key risk indicator (KRI). It's an indicator that something unusual is happening on the network that could be a sign of an increased risk, such as a denial-of-service attack or unauthorized activity.

It's not a threat (A) itself, but a potential sign of a threat. It's not a risk event (B) yet, but it could indicate an increased likelihood of a risk event. It's not a lag indicator (C) because it's alerting in real-time, not after the fact.