Japanese law enforcement authorities have taken down what they claim to be a massive spam operation responsible for sending out more than five billion junk emails over a two-month period in the summer of 2006. A total of four men were arrested including Yoshimitsu Hirono, president of large Japanese dating site Takumi Tsushin, based in Tokyo.

The police believe he was responsible for the orchestration of a massive spam operation that saw tens of millions of people receiving unwanted messages every day in July and August last year. In order to carry out their mass mailing the group built and operated a 128-strong computer cluster that was physically located in China and was remotely accessed from Japan. It was used to mass-mail advertising material for Hirono’s dating site utilising a huge illegal database of Japanese email addresses. The Takumi Tsushin dating site is believed to have significantly profited from the spamming operation, boosting client numbers and making up to $1 million every month. Police say the four men who were detained in connection with this case have already admitted their guilt.

According to a report in the Daily Mainichi, the spamming group used China as a base not only to cover their tracks, but also because running costs there are much lower. Over the past years China has consistently performed as one of the top spam-relaying countries, second only to the US.