As part of the BBC’s Click programme, BBC researchers acquired a low value botnet and used it to demonstrate how botnets can be used to send spam and perform denial of service attacks. …
http://www.h-online.com/security/The-BBC-acquired-a-botnet-but-was-it-legal-Update--/news/112834
See also:
http://news.bbc.co.uk/2/hi/programmes/click_online/7932816.stm
http://news.bbc.co.uk/1/hi/technology/7938949.stm
http://news.bbc.co.uk/2/hi/programmes/click_online/7884387.stm