That grim assessment is contained in an unclassified DHS intelligence memo prepared for various law enforcement groups, which says terror groups are expected to try attacks inside the United States with “increased frequency.”

CNN obtained a copy of the document, dated May 21, which goes on to warn, “we have to operate under the premise that other operatives are in the country and could advance plotting with little or no warning.”…

The report say U.S. officials “lack insights in specific details, timing and intended targets,” but trends indicate terrorists are looking for “smaller, more achievable attacks against easily accessible targets.”