ISIS attacks: How are claims of responsibility verified?

The recent wave of attacks, from Turkey toBangladesh to Saudi Arabia,hasraised fears that the Islamic State of Iraq and Syria (ISIS) is on arampage and that's exactly what the group wants, terrorism experts say.

"ISIS is showcasing its geographic reach," saidKamranBokhari, a fellow at TheGeorge Washington University's extremism programand a senior lecturer at the University of Ottawa.

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Claiming responsibility forthe attacks even if they'recarried out by affiliated groups not necessarilydirected by ISIS leadershipis astrategicmove, Bokhari said.

"It creates the perception that ISIS is expanding, even though it's under attack on multiple fronts in both Iraq and Syria," he said. "That creates this sort of panic and that works to the advantage of ISIS."

"The PR's important," addedScott Stewart, vice-president of tactical analysis forStratfor, a geopolitical intelligence firm based in the U.S."There are two battlefields: you have the physical battlefield and kind of the ideological or the media battlefield."

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So if it's in ISIS's interest toclaim responsibility,how do authorities know the group isn't putting its stamp on attacks it had nothing to do with?

"Contrary to popular opinion, they don't take credit for attacks they haven't directed themselves,"said Amarnath Amarasingam, a terrorism expertat Dalhousie University and also a fellow in the extremism program at The George Washington University.

ISIS claimed responsibility for a suicide bombing that killed at least 250people in a Baghdad shopping district last weekend, as well as the execution of 20 hostages at a restaurant in Dhaka, Bangladesh, the weekend before.

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No grouphas claimed responsibility for three separate bombings in Saudi Arabia on Monday, but ISIS is widely suspected. Terror experts also believe a group affiliated withISIS is responsible for theIstanbul airport attack in Turkey that killed more than 40people in June.

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The gunman who killed 49 people at thePulse gay nightclub in Orlando, Fla., last month claimed to be acting on behalf of ISIS. Amarasingam said in ISIS "inspired attacks" like that, the group only takes credit "once they are confident that the attackers have indeed given allegiance."

The Bangladeshi government denied that ISIS was behind the Dhaka restaurant killings and police said the attackers were part of a domestic group calledJumatul Mujahedeen Bangladesh (JMB).

But that doesn't mean they weren't affiliated with ISIS, said all three terror experts interviewed by CBC News.

"There is a political imperative on the part of the Bangladeshi government to say 'we don't have ISIS here,'" Bokhari said, noting that ISIS is competing withal-Qaeda for influence in the South Asiancountry.

"Bangladesh is a strategic location," Stewart said. "Both the Islamic State and al-Qaeda would love to lay claim to it as, you know, their turf."

It is vital to recognizethedifference between attacks by "grassroots jihadis" and thosedirected byISIS's core in Iraq and Syria,Stewart said.

"Islamic State is not necessarily the cohesive organization they would like you to think they are," he said. "A lot of these attacks really aren't very sophisticated."

"[ISIS leader Abu Bakr] al-Baghdadi's not sitting there at a big three-dimensional chess board pulling all these things together."

'Ripping into the identity' of attackers

Both Stewart and Bokhari said forensic investigations, often conducted by U.S. government agencies whenISIS involvement is suspected, play a big role in verifying claims of responsibility.

"[Investigators]go back and trace the steps of the perpetrators," Bokhari said. They try todetermine where the money that funded the attack came from, who trained the attackers, who organized the logistics and comb through cellphone records and internetbrowsing histories to see"who was talking to whom."

"You're ripping into the identity of the attackers," said Stewart, who conducted terrorism investigations as a special agent with the U.S. State Department for 10 years."That's going to let you know basically who they were working with and for."

Sifting through the rubble in the aftermath of an attack also yields important clues, he said. For example, findingchunks of an explosive device and figuring out how it was constructed can reveal the "signature of the bombmaker."

"Identifying key people in the organization whether it's a bombmaker, whether it's an operational planner, those are the people that you need to identify and then try to go after," Stewartsaid.