As you've no doubt heard, some fellow keen on moving up to the top spot on the president's drone-strike authorization checklist advised the noble warriors to prove their righteous manliness with a mass attack at the Mall of America, among other places. Opinions on the threat's credibility vary, but the head of Homeland Security said we should be "particularly careful."
You assume that term was chosen for a reason. Not careful, but particularly careful. Perhaps there's a sliding scale.
No threat: General carelessness.
Slight threat: Take care sporadically.
Elevated threat: Be careful, especially on the escalators.
Vague but credible threat: Be generally careful.
Credible specific threat: Be particularly careful.
Holy cow, something's up: Be specifically careful as well as particularly careful.