An alarm for digital storage discs includes an alarm module positioned within the central indention found in conventional CD and DVD jewel cases. A lid sensor in communication with the alarm module includes a pair of spaced trigger arms that form an ovate opening. A nodule on the uppermost arm engages the jewel case lid to maintain engagement of electrical contacts on the arms. An arming switch includes a magnetically-operated pin that is extended into the opening formed between the triggers to prevent the contacts from separating. Once the jewel case is sealed, an arming station initially retracts the pin while the case lid firmly engages the nodule to maintain the contacts in engagement. If an unauthorized user opens the jewel case without first extending the pin at the arming station, the triggers will automatically separate thereby activating the alarm.