This is the first signal that something is wrong. It shouldn't reveal the whole picture, but it should disrupt the normal routine or baseline operations.
Show who is receiving the alert, how they feel, and what immediate, prescribed action they are forced to take. triple alert
Five minutes later, the automated fire suppression system reports a sudden spike in ambient temperature, or data loss prevention software flags an massive, unauthorized file transfer. 3. The Climax (Alert 3: The Critical Point) This is the first signal that something is wrong
A motion sensor trips in a restricted server room, or a security dashboard flags a single anomalous login from a remote location. 2. The Rising Tension (Alert 2: The Complication) Five minutes later, the automated fire suppression system
Keep it subtle but undeniable. This creates curiosity or initial concern for your characters (or incident responders).