Chinese police have detained more than 250 people suspected of operating unlicensed telecommunication installations used to send spam to nearby mobile users. The Ministry of Public Security (MPS) said on Tuesday eight manufacturing dens of such devices were destroyed in 16 major cases, with nearly 230 sets of equipment confiscated over a period of two months. The campaign against fake base stations started in February and targeted installations that allow spam with fake phone numbers or disguised as official communications to be sent to nearby mobiles. Chinese mobile users received over 300 billion pieces of SMS spam last year, based on analysis of 270 million complaints, according to a report of the People's Daily on April 12. Nearly 100 billion messages are fraud, gambling scams and promotions, according to the MPS. According to Zhao Yimin, of the Shanghai police, fake base stations are a profitable business. One station makes about 120 yuan(19.2 U.S. dollars) per hour by sending 12,000 pieces of spam. The cost of a set of fake base station is between 14,000 yuan to 22,000 yuan, according to Zhao.