"Social network analysis is an important tool," National Security Adviser M K Narayanan told rediff.com recently.

"I don't think anyone is interested in picking up Muslims or Hindus or anyone else for that matter after an incident (of terrorism)," Narayanan said, "Whenever an incident takes place we have a whole set of methodologies that are followed."

"If you are a friend of x (a likely suspect) and if an incident takes place," the national security adviser explained, "you come under the scanner. There is a certain relationship between x and y and z and the police have to willy nilly examine it."

The Hyderabad police is said to have picked up several youth after the August 25 blasts in the city on suspicion that they may have information about the terrorists who killed 42 people and injured scores of others.

Narayanan said that scientifically it has been proved that between the perpetrator of an incident and his friends and accomplices there is at the utmost only six levels/degrees of separation "If you are involved, then a friend of yours will come within the orbit of suspicion," he said.

"Social networking is a scientific tool that was not used so much in intelligence until recently," the national security adviser added, "We are now using it fairly extensively."

Another tool also being employed by the intelligence agencies is spectrum analysis. Analysts at intelligence agencies study an entire spectrum of incidents -- where, what, why, how -- and then come up with a likely map of locations where terrorism is likely to occur.