The Pentagon Force Protection Agency has sent out warnings to troops saying they should “mask their identities” and change their routines, warning they risk attack by ISIS.

“Terrorists directed or inspired by ISIS view members of US military and law enforcement officers as legitimate targets for attack,” the memo warned, adding that attacks could have “little-or-no advanced warning.”

The warning appears to stem from the Ottawa parliament attack earlier this month, and the belief that ISIS and its sympathizers could be keen to attack military targets as they find them, particularly as the war escalates.

The memo urged soldiers not only to vary their travel routines, but to take any military decals off their vehicles, and to avoid posting anything critical of terrorist organizations on social media, on the notion that it might fuel such attacks.

There’s no doubt that ISIS, or indeed any terrorist group that the US is openly at war with, would consider US troops to be a legitimate target, but the memo suggests a level of concern about it that underscores just how little of a handle the US intelligence community has on the possibility of lone wolf attackers.