Which INFOCON level mandates disconnection of all unclassified dial-up connections?

INFOCON, or Information Operations Condition, is a system used by the Department of Defense to indicate the current risk level from cyber threats, dictating operational responses to those threats. The various INFOCON levels range from one to five, where a lower number indicates a higher threat level.

INFOCON 3 is the level that primarily focuses on precautionary measures to safeguard unclassified networks. It is characterized by an increase in the level of operational readiness to respond to potential attacks or incidents, and it recommends disconnection of all unclassified dial-up connections to mitigate risk against potential cyber threats. This action is taken to limit vulnerability in the face of known or suspected adversarial activities.

The other INFOCON levels serve different purposes: INFOCON 4 indicates a decreased level of threat and allows more connectivity, while INFOCON 2 suggests a significant threat requiring immediate actions to safeguard operations but may not mandate total disconnection of dial-up connections. INFOCON 5 reflects a normal readiness posture, meaning the threat level is minimal. Thus, the correct choice is INFOCON 3, as this level specifically emphasizes the need to sever all unclassified dial-up connections as a protective measure against cyber risks.