Three of the prisoners ISIS apparently wants back are women -- a failed suicide bomber, an alleged bomb maker and a woman tied to the head of ISIS. The fourth is a child.
Many countries have a strategy of not negotiating with terrorists.
But this new approach by ISIS is putting governments to the test.
In its most recent demand, ISIS called for Sajida al-Rishawi to be handed over. She is a female Jihadi imprisoned for her role in a 2005 suicide bombing at a wedding reception in Jordan that killed dozens.
If she wasn't brought to the Turkish border by sunset Thursday, the militants said, two hostages would die: Japanese journalist Kenji Goto
and Jordanian pilot Moaz al-Kassasbeh
. The deadline has passed but the hostages' fate is unknown.
"By negotiating with ISIS, by recognizing them, by even having dialogue with them, it gives them the impression of acting as a state," said Sajjan Gohel, international security director at the Asia Pacific Foundation.
Jordanian officials have said they are willing to swap al-Rishawi for the pilot. But they have demanded "proof of life" to demonstrate that al-Kassasbeh, captured in December after his fighter jet crashed in Syria, is still alive.
Former FBI negotiator Chris Voss said Jordan was absolutely right to do so -- and that the failure of ISIS so far to provide proof of life was suspicious.
"It's just a natural and ordinary course of bargains in these types of negotiations and they are choosing not to do that at this point," he said.
The latest proposal by ISIS is not a prisoner exchange in the usual sense -- since the militants now want the release of al-Rishawi just in order not to kill the two hostages, rather than promising their release.
Voss said entering into this kind of territory with terrorists was dangerous
"If you engage in that sort of bargain then they can threaten to kill the same person over and over and over again -- and continue to demand release of hostages or whatever their demands are," he said.
"You can't give in to that sort of thing because then it puts you in an endless loop where they have all the power."
It's important to remember that for ISIS and groups like them, the key factor is gain, Voss said.
"Kidnappers are in a commodities exchange business. While it's a horrifying concept to us, to them it's business -- and it's the business ISIS is in and so you have to treat it like that."
Symbolically important prisoners
Besides failed suicide bomber al-Rishawi, ISIS wants two other women -- an alleged bomb maker and a woman tied to the head of ISIS -- and a child.
Each of the prisoners is symbolically and strategically important for the terror group.
Al-Rishawi is connected to ISIS through her brother, once a ranking member of al Qaeda in Iraq, which spawned ISIS.
In exchange for American journalists James Foley and, later, Steven Sotloff -- ISIS demanded the release of Aafia Siddiqui, nicknamed "Lady Al-Qaeda" -- an imprisoned neuroscientist in the United States, linked to 9/11 mastermind Khalid Sheikh Mohammed.
She was arrested in Afghanistan in 2008 carrying bomb-making documents for a "mass casualty" chemical and biological weapons attack against American targets including the Statue of Liberty and the Brooklyn Bridge.
One high profile prisoner who ISIS has not yet publicly demanded is Saja al-Dulaimi
. She may be the wife of shadowy-ISIS leader Abu Bakr al Baghdadi, who fought with al Qaeda in Iraq, though the Iraqi Interior Ministry has disputed that.
Regional sources have told CNN that al-Dulaimi is herself a powerful ISIS figure, arrested as a high value target as she crossed into Lebanon with a four-year old child, whom one intelligence source identified as Baghdadi's son.
Since their capture in March 2014, Baghdadi has been calling to get his child released, a regional source said.
In the past, in similar cases, governments have budged.
Last year, the United States traded several Taliban captives for Sergeant Bowe Bergdahl, who was captured by the extremist group almost five years earlier.
Despite claims that Bergdahl may have abandoned his post before being kidnapped, the State Department defended the move, saying it was nothing unusual.
"It is consistent absolutely with what's happened in previous wars -- including Korea, including Vietnam," said State Department spokeswoman Marie Harf, adding that there was "a long history in the United States of prisoner swaps."
Complicating the debate, one of the five Taliban detainees
released from Guantanamo Bay in return for Bergdahl last May has attempted to return to militant activity from his current location in Qatar by making contact with suspected Taliban associates in Afghanistan, multiple officials told CNN on Thursday.
During the Cold War, the West also swapped hundreds of spies with Communist bloc countries.
But prisoner swaps with extremist groups remain controversial.
In 2011, Israel made a major made a major concession to its arch enemy, the Palestinian militant group Hamas, which runs Gaza.
It exchanged more than 1,000 Palestinian prisoners in return for the soldier Gilad Shalit, who had been kidnapped in Gaza in 2006.
Hamas celebrated the deal as a major victory and the government of Prime Minister Benjamin Netanyahu was heavily criticized.
Ransom or swap?
Duncan Bullivant, a UK-based risk consultant, says swapping prisoners for hostages is still better than paying for release of prisoners, as some European countries do.
"The payment of cash ransom can been seen as the direct funding of terrorist organizations and for that reason and a few others, is regarded as unacceptable certainly by the U.S., UK and increasingly other nations," he said.
"There would be nothing unusual about the swapping of combatants and if the Japanese victim is thrown in as part of the deal, then that is a great bonus."
It's sadly far from certain that Goto and al-Kassasbeh will emerge from the current negotiations alive.
But whether they gain the release of al-Rishawi or not, ISIS' leaders have very clearly achieved one goal: maximum media coverage for their cause.