On 20 March 2013, three South Korean television stations and a bank suffered from frozen computer terminals in a suspected act of cyberwarfare. ATMs and mobile payments were also affected. The South Korean communications watchdog raised their alert level on cyber-attacks to three on a scale of five. North Korea has been blamed for similar attacks in 2009 and 2011 and was suspected of launching this attack as well. South Korean officials linked the incident to a Chinese IP address, which increased suspicion of North Korea as "[i]ntelligence experts believe that North Korea routinely uses Chinese computer addresses to hide its cyber-attacks."