The Intelligence Bureau says all terror strikes are executed through sleeper cells, with the latter either directly involved in the attacks or, two, by providing logistical support to those who carry out the attacks.

The IB provides the example of Afsar Pasha, a terror suspect arrested in Karnataka who disclosed a plan to blast the Vidhan Soudha and other key installations in Karnataka, to explain how the network operates.

Pasha was the member of a sleeper cell in Karwar, coastal Karnataka, and worked as a mechanic. The IB says most sleeper cell operatives hold a regular job for most part of the year. Arrests across the country show that most of the youth who are part of sleeper cells work as mechanics, STD booth operators and, in some cases, insurance agents.

The IB points out that these jobs involve meeting a lot of people which in turn helps them gather data. Of late, there is also an increasing trend to recruit educated youth. However, their role is largely restricted to data collection and improvising techniques during terror strikes, says IB.

Mechanic Afsar Pasha revealed during his interrogation that his initial job was largely confined to gathering data and providing logistical support. However, as he gained more experience, he was directed to take part in field activities, meaning he had to actively take part in terror strikes.

The IB says based on the interrogation of several terrorists they have gathered considerable information regarding the working of sleeper cells. For the most part they remain inactive, apart from collecting data, training cadres and doing recruitments. The data is passed on to their supervisors through e-mail and/or on the telephone.

Once the decision is taken to strike, a couple of members from the sleeper cells are chosen to carry out the attack. The persons undertaking the attack are known as foot soldiers, the IB says.

A set pattern is that members of local sleeper cells are usually not the ones who carry out an attack in their jurisdiction. A person from another sleeper cell is sent in for this, with the local member only providing logistical support.

The IB also says members of sleeper cells work as a close-knit group. Normally, in a serial terror strike, nearly 10 people are involved. While a team of five would plant the bombs, two work as a back-up and the rest would provide data.

The IB says there is a general belief that the sleeper cells are housed away from the main city or town area, and in busy market areas so that the members can blend in with the crowds. An IB document states, 'It is not necessary for visiting terrorists to make a beeline to the... (local rendezvous points). The handlers from their intelligence agencies provide them with a blueprint of hubs or cells.'

The IB further states that the sleeper cells which are patronised by Pakistan are mainly involved in collection of geographical and geo-strategic information. Until a few years back these cells only undertook intelligence-related work, but with the Indianisation of jihad gaining ground, sleeper cells have been directed to carry out the attacks.

The IB says the functioning of sleeper cells could be summed up as: