Simultaneous attacks on public transport. Blasts timed to key political events. Claims of responsibility on Internet sites.
The London terror attacks bear the stamp of al Qaida, but terrorism experts say Osama bin Laden may have played little or no role. They suggest that what's far more likely is that the attackers who planned and carried out the bombings were local operatives who didn't need much money or expertise from overseas to wreak havoc.
"I think its home-grown definitely," said Loretta Napoleoni, author of Terror Incorporated: Tracing the Dollars Behind the Terror Networks. "This is a new generation."
Experts are looking closer to home because of the relatively small scale of the operation - four bombs each containing less than 4.5 kg of explosives, according to police. Such an attack wouldn't require funding from outside the country, allowing the bombers to avoid international bank transfers that might have prompted suspicion.
Larger operations, like the Sept 11 attacks or the bombing of the USS Cole, are complicated and expensive, requiring huge infusions of cash to purchase equipment and move operatives around. Napoleoni estimates the attacks cost between USD 10,000 and USD 15,000.
"They do not have unlimited resources," she said.
"They adjust the model to how much money they have. If they could have raised more money, they would have had more explosives."
What's more, the bombers understood London knowing which subway lines to hit and targeting trains while they were between stations to inflict maximum damage.