The Department of Homeland Security has been forced to release a list of keywords and phrases it uses to monitor social networking sites and online media for signs of terrorist or other threats against the U.S.

The intriguing the list includes obvious choices such as 'attack', 'Al Qaeda', 'terrorism' and 'dirty bomb' alongside dozens of seemingly innocent words like 'pork', 'cloud', 'team' and 'Mexico'.

Released under a freedom of information request, the information sheds new light on how government analysts are instructed to patrol the internet searching for domestic and external threats.