With the national terror threat level now on orange (high), the Department of Homeland Security (DHS) is implementing sweeping security measures that include tighter border and transportation checks, monitoring of food plants and wider use of armed sea marshals on ships, according to DHS Secretary Tom Ridge.

Detailing the comprehensive national security plan, known as Operation Liberty Shield, Ridge said March 18 that it was "the first, and to date, most dramatic example" of the DHS "working with our national partners, state and local government and the private sector."

Ridge said the government would do "everything possible to minimize inconvenience to citizens and disruption to commerce."

CEOs of leading U.S. companies were taking steps to protect their employees and facilities, according to Tita Thompson, spokeswoman for the Business Roundtable, a Washington, D.C.-based association of about 150 CEOs from very large U.S. companies.