It's not the National Security Agency you should be worried about spying on smartphones. Ordinary people are using sophisticated software to eavesdrop on conversations of their lovers, children, and business rivals.

A new study that examined the data traffic of mobile devices operating on the Middle Eastern network of a European carrier found that hundreds of people had some form of surveillance software installed on their phones.

The apps aren't malicious ones that users had to be tricked into downloading. Instead, they're pieces of commercially available spyware that people with physical access to the devices have installed to secretly log each text message, phone and contact - and in some cases, to eavesdrop calls in real time.

According to Michael Shaulov, CEO of Lacoon Mobile Security, many of the installations were mostly done by spouses and private investigators. The number of phones with spyware was relatively small (more than 600), but Shaulov expects the figure to grow amid increasing awareness of surveillance technology - be it at a consumer or national level.

Lacoon does research and development in Israel. The San Francisco-based startup sells security software that detects malicious mobile apps and attacks on corporate networks.