Phone tapping in India has become a national concern with a leading operator revealing that at peak there are upto 100 phone tapping requests a day. In India there are ten major operators, at a conservative average of 50 taps a day per operator, there would be 182,000 authorized phone taps each year. There are six ways in which modern phone systems can be illegally tapped for corporate espionage and spying: Use of Over the Air technology. Unauthorized use of the Lawful Interception System in Telecom companies can use the telecom company’s lawful interception system to illegally tap phone and delete any audit trails.
Source: https://thehackernews.com/2011/02/six-ways-your-phone-can-be-illegally.html