Team Poison have promised to support activists looking to protest against the US government on 11 September with attacks against its agencies.
In a message posted on document sharing web site Pastebin, the hackers announced Op911 and explained that they plan to protest against what they claim was an "Inside Job".
"9/11/2011 will be the 10th anniversary of the september 11 attacks. We the people will take to the phone lines and protest against the inside job that led to thousands of innocent people being killed," they wrote.
"On 9/11 phone the numbers bellow and say:
"Dear USA, your 9/11 is our 24/7, Sincerely. [a country that has been bombed/attacked by USA]. so; e.g: "Dear USA, your 9/11 is our 24/7, Sincerely. Iraq".