The American military has stepped up security measures at installations around the country in response to growing concerns about "homegrown violent extremists," a U.S. defense official said. The commander of the U.S. Northern Command sent an advisory Thursday night directing all commanders in the United States to tighten up protection, the official said. The increased security is not specifically tied to a threat from ISIS, but it is based on recent intelligence FBI Director James Comey mentioned earlier this week regarding the collection of information on people in America who sympathize with ISIS and other Islamic terror groups.
