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Who Is Being Tapped:

Often a hint of suspicion can put you under the scanner. Home ministry officials became suspicious of the flamboyant lifestyle of IAS officer Ravi Inder Singh. The bureaucrat shunned his official accommodation in favour of a plush guesthouse provided by his friend and co-accused Vinit Kumar. Singh's phones were kept under observation where he was heard referring to "Ukranian and Russian software", a code for prostitutes. Hotels were referred to as hardware and bribes were called laddoos.

He was charged with giving clearance to a US-based telecom company, Telecordia, for mobile number portability. Dozens of other bureaucrats are believed to be under surveillance for similar reasons. But for every legal case, there are hundreds of illegal wire taps. Five years ago, a Mumbai newspaper publicised explicit phone conversations of actor Salman Khan.

The Government claimed the voice on the tapes was not Khan's. It was a cover-up of an illegal wiretap. The conversations had been leaked out from the city crime branch. Four private detectives were arrested for illegally obtaining phone records of former Samajwadi Party leader Amar Singh in 2005.

But what if an illegally monitored phone yields evidence of wrongdoing? Officials say a backdated application is sought from the home secretary.

How They Are Tapped:

Every agency fills out an authorisation slip before placing a phone under surveillance. In the states, it is the state home secretary who signs this. Officially, telephones of politicians cannot be tapped-a qualifier on the slip says the surveilled person is not an elected representative.

Before the advent of cellular phones, state agencies often strung out parallel lines from telephone poles, rented lodgings in the vicinity or even pitched a tent in the vicinity posing as nomadic tribes. Often the target would get to know due to the disturbance in the phone. Calls could only be listened to, not recorded. Cellphones gave organised crime syndicates mobility and anonymity as connections could be bought in fake names. In the mid-1990s, operators were ill-equipped to intercept calls.

In the first instance of surveillance, the then deputy superintendent of the Uttar Pradesh Special Task Force (STF) Rajesh Pandey got a telecom engineer in Allahabad to devise a typewritersized interception box. The box was lugged around and connected to switching stations.

Today, every cellular service provider has an aggregation station which is a clutch of servers called mediation servers (because they mediate between the cellular operators and the law enforcement agencies) to intercept phones. Two kinds of interception facilities are available-Integrated Services Digital Network (ISDN) and the leased line. Under ISDN, a mediation server intercepts a call, and then transmits it through a Primary Rate Interface (PRI) line to the office of a government agency.

The police can listen to the phone on their PRI line and store the recording to attached computers. Simultaneously, a sound file of the intercepted call is also recorded and stored in the mediation server. In ISDN, the transfer of call-related data doesn't happen in real time. A slow 64 KBPS speed results in a time lag of two to three minutes. Data packets are lost in traffic and calls don't reach the PRI line.

Under the leased line facility, the service provider gives the agency direct access to its backbone network through a dedicated fast speed fibre optic cable connection. The call-related data is not only transmitted in real time, at the lightning speed of 2 MBPS, the chances of missing any call are minimal.

But since the cost of laying a fast-speed fibre optic cable connection is higher, state agencies are more dependent on ISDN. For instance, the Mumbai Crime Branch has leased line connections from just three service providers, for the rest it uses ISDN. At any given point of time a service provider can provide a maximum of eight agencies the call interception facility to a given number.

The commonest surveillance methods are sourcing an individual's call data records (CDR) or list of numbers dialled and received. This does not require government sanction. Fed into a special software, the CDR rapidly builds up a 'relationship tree' or charts the relationship between thousands of calls. This can easily be used to pry on civilians. A secretary in a Central ministry is believed to source the CDRs of journalists to trace their sources.