A PIL by one Ravindra Kumar had alleged that the government and probe agencies indiscriminately intercepted telephones without following procedure.
The government denied the charge but clarified, "With the advancement of wireless networks worldwide, many eavesdropping techniques have also been developed."
Dealing with politician Amar Singh`s allegation about illegal interception of his phone, a bench comprising Justices G S Singhvi and A K Ganguly said, "It is more serious. If a service provider connives with a private person and starts intercepting telephones, then it is very dangerous. Anyone can go to the service provider and listen to the conversations."
Attorney general G E Vahanvati shared the court`s concern and said a service provider need not even be approached. He said technology had advanced to such an extent that one just needed to download the software from the internet and feed the mobile phone pin number in it to listen and record the conversations.
"People are eavesdropping on many conversations. It is a serious problem. I am seriously concerned about it," the AG said.
The government's affidavit said the present encryption algorithm, technically termed A5/2, used by global system mobile (GSM) service providers to transmit conversations from one phone to another, was weak in security. "A few have upgraded to A5/1, which provides higher security. Newer technologies such as 3G envisage further advanced algorithm," it said.
It clarified that government orders for interception "essentially relates to telephones of persons involved in terrorist activities, economic offences, drug trafficking, money laundering and other criminal activities or for preventing the commission of an offence".
It said eight central agencies and police of all state governments have the power to intercept telephones. Union home secretary permits the Central security and law enforcement agencies to intercept phones, while the state police seek permission from their home secretary.