According to information leaked by Edward Snowden and reported by the German publication Der Spiegel, the NSA (National Security Agency) “has been systematically eavesdropping on the Mexican government for years.” 

explains more at Boing Boing:

A Snowden leak, discussed in detail in Der Spiegel, shows how the NSA broke into the email servers of the Mexican president Felipe Calderon's public account, and used that access to wiretap the president, cabinet members, and senior diplomats. The NSA described the program, called “Flatliquid” as “lucrative.” A second program, “Whitetamale,” also spied on senior Mexican politicians (including presidential candidate Peña Nieto), targeting efforts to change the country's disastrous War on Drugs.

The Guardian reports that Mexico's foreign ministry condemned these allegations and stated that “this practice is unacceptable, illegal and against Mexican and international law.” The foreign ministry also said that “US President Barack Obama had pledged to carry out an ‘exhaustive investigation’ into who was responsible for the suspected spying.”