The U.S. Department of Homeland Security says state and local law enforcement are also making security changes they deem appropriate.
"There are also a number of other security measures we are taking that are not suitable for public disclosure," Secretary of Homeland Security Jeh Johnson said in a prepared statement.
Johnson also stressed the importance of speaking up about suspicious behavior.
"Public awareness and vigilance are vital to our homeland security efforts, and have in fact prevented terrorist or criminal acts in the past. In today's environment, we urge the public to continue to travel, visit public events and places, and continue with their daily lives, but at all times be aware and vigilant," Johnson said.
You may report threats of suspicious activity to the FBI or your local authorities. Information about how to contact an FBI Field Office can be found here. Community leaders, co-workers, friends and family can help by recognizing signs of potential radicalization to violence.