The corps issued an order Monday saying the ban is effective immediately on the Marine Corps computer network. It said the Internet has been used as a haven for malicious behavior, and said that using social sites can expose information to adversaries.
The Associated Press has learned that the move is part of a larger Pentagon review. Deputy Defense Secretary William Lynn last week ordered a review of both the threats and benefits of using social networking -- and asked it be done by the end of the month.
The order doesn't effect Marines' private use of such networks on personal computers outside of their jobs.