SMS spam (sometimes called cell phone spam) is any junk message delivered to a mobile phone as text messaging through the Short Message Service (SMS). The practice is fairly rare in North America, but has been common in Japan for years. In 2001-2002, the systems at DoCoMo, the country's major service provider, were overcome by the volume of SMS spam, causing users' screens to freeze and spreading programs that caused the phones to dial emergency numbers.
Text messaging has greatly increased in popularity in the past five years and the government is trying to keep up with rapidly changing technology. Although SMS spam is less prevalent than email spam, it still accounts for roughly 1% of texts sent in the United States and 30% of text messages sent in parts of Asia. In the United States, SMS spam messages have been illegal under the Telephone Consumer Protection Act since 2004. Citizens who receive unsolicited SMS messages can now bring the solicitors to small claims court. In 2009, China’s three main mobile phone operators (China Telecom, China Mobile Ltd and China Unicom) signed an agreement to combat mobile spam by setting limits on the number of text messages sent each hour.