BBC reporter Spencer Kelly and security company PrevX took over an existing botnet of approximately 22,000 computers, and used them for their spam experiment. They ordered the innocent third-party computers to send 500 spam messages each to Hotmail and Gmail accounts under the control of the BBC. The BBC and PrevX did not have the permission of the computer users to send those spam mesages. This is clearly an unauthorised modification of computer data, and is to my mind a breach of the Computer Misuse Act.”]
Source: https://nakedsecurity.sophos.com/2009/03/12/bbc-break-law-botnet-send-spam/