A surge in Chinese visitors to the United States during Lunar New Year celebrations last year offers a clue to the scale of American spies' wiretapping of citizens in China.
According to a report on privacy breaches by the US National Security Agency, leaked by whistle-blower Edward Snowden and published by The Washington Post yesterday, an 11 per cent rise in "roamer" incidents in the first quarter of last year may have been caused by the annual Chinese holiday.
These incidents are when a "valid foreign target" whose mobile phone is being wiretapped without a warrant lands on American soil.
The target becomes active in the US when they land and an individual warrant is needed to continue the wiretap, or else it would be a breach of US laws which protect the communications of Americans and others while they are in the country.
The report, which tracked accidental and deliberate breaches, said that the rise in roamer incidents between January and March last year "may be attributed to an increase in Chinese travel to visit friends and family for the Lunar New Year holiday".
The classified audit was part of a number of wider leaks made by Snowden in June this year which exposed the domestic and global reach of the NSA's cyberspying programmes.
Snowden further claimed, after he broke cover in Hong Kong, that US spies had been hacking into computers and mobile phones in Hong Kong and mainland China for years.
The audit separated the violations into two categories: those in breach of the Foreign Intelligence Surveillance Act and those that flouted Executive Order 12333, which gives more power to spy agencies.
In the 12 months to March 2012, the NSA broke privacy rules or overstepped its legal authority 2,776 times through the unauthorised collection, storage and access to, or distribution of, legally protected communications, The Washington Post reported.
The NSA did not deny the report but rather offered a more positive interpretation. It said it had rigorous procedures in place to review any breaches of privacy and that most of the errors were inadvertent and due to technical glitches.
"NSA's foreign intelligence collection activities are continually audited and overseen internally and externally," the agency said in a statement
Meanwhile, the Hong Kong government said US officials had still not responded to a letter sent in June which sought answers to Snowden's claims that US spies had hacked the city's computers.
Macau officials are also waiting for a response to a letter demanding answers over hacking claims, which was sent to the US consulate on July 3.