That is a good question, Velveeta. No way to tell for absolutely certain, other than it appears to be signed "al qaeda."
Both the message and sign-off do not mention the "Brigades" group that released the reminder warning to Italy last month just prior to the end of usama's stated deadline. The Brigades group also is the same group who took credit for last year's August blackout.
Curious. I thought the official we-can-threaten-Italy-group was the Abu Hafs al Masri brigade. I guess we wait.