The public outcry over the NSA and surveillance techniques revealed by Edward Snowden did nothing to hamper phone manufacturers' research into call interception and monitoring technology; in fact inventions in the space have risen dramatically, a study of patents filed has found.
Almost 3,000 call monitoring, cellular privacy and or anonymity patents have been filed since 2010.
Caller privacy technology has always been a lucrative business for security within enterprise and governmental confidentiality. However technology to actively intercept and monitor calls is growing steadily, a study by Thomson Reuters found.
While only 100 patents for call monitoring were filed in 2010, it increased to 1,000 in 2014.
Phone manufacturers are at the forefront of the trend but Google, Fujitsu and Intel names are present on the patent files.
Chinese multinational phone firm ZTE Corp filed the most patents (160), focusing on sms privacy, law enforcement call monitoring and encryption, however, it has not filed as many iterations to its product as LG, AT&T and Nokia.
Ericsson, Blackberry and Qualcomm boast the most highly-cited patents in the field, while LG, AT&T, and Nokia also have more citations than their number of inventions would indicate an expert knowledge of the area, and a good option for firms looking to secure their mobility strategy.
Another Chinese firm Huawei, which was notoriously ousted from the US following a spying controversy, is working in the area.
Huawei, which has supplied networking equipment to BT since 2005 was subject to a parliamentary committee investigation three years' ago, after the US refused to work with the corporation as it posed a threat to its own national security, it alleged.Read more: Google, Microsoft serve up security treats for productivity suites
A US government report found that Huawei had links to the Chinese Liberation Army and was subject to government requests, fuelling spying rumours.
The major handset player ranks below Blackberry (which is focusing on smartphone applications and global secure access amongst its 100 patents), Ericsson and Qualcomm for call monitoring development. However, it is one of the firms to most recently increase its product patents, alongside Ericsson who filed the most patents in 2014. ZTE and Blackberry, for instance, have a higher volume of patents, but the majority were filed in 2011 and have now slowed.
Nokia, Samsung and Alcatel Lucent are also working on similar inventions.