MANHATTAN - Homeland Security Secretary Janet Napolitano appeared in Manhattan this morning to unveil a new terror alert system to replace the color-coded five-level system that had been in place since 2001.

The new system consists of two levels, "elevated" and "imminent." The former will mean there is a "credible" threat against the U.S., while the latter will mean there's a "credible," "specific" and "impending" threat.

The government will also issue the alerts through Twitter and Facebook in addition to conventional media outlets.