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A little-known federal program that doles out millions for tips on terrorists is now in the spotlight after lawmakers questioned how it was being employed in the Benghazi attack investigation.

State Department officials revealed recently, despite lawmakers being kept in the dark, that they’re quietly offering a multi-million dollar monetary sum through the “Rewards for Justice” program for information leading to the suspects in the Sept. 11, 2012 attack.

The admission prompted Republicans to question how effective the hush-hush offer can really be. Despite the current dispute, a look back at the decades-old program shows it’s been used repeatedly in the past to help bring wanted terrorists to justice -- while making some fortunate tipsters very rich in the process.

The program is set up similar to the FBI’s “Most Wanted” list, and has netted several accused high-profile terror leaders by offering huge sums for information on them.

In most cases, payments are capped at $5 million or less. The reward for tips on 12 of the most wanted in Afghanistan ranges from $20,000-$200,000.

To date, RFJ has paid more than $125 million to 80 informants, according to the State Department. The program has helped track down, capture or kill 12 terror leaders, including Ramzi Ahmed Yousef, the man who plotted the February 1993 World Trade Center bombing.

In most cases, the federal government cannot disclose who made the tip.

"They're putting themselves at great risk," a State Department official said of the tipsters.

But the official told FoxNews.com the payouts have increased since the Sept. 11, 2001 attacks. "If nothing [else], I think awareness of terrorism definitely went up," the official said. "People took it as a scourge that really must be stopped."

During the Persian Gulf War, one tipster from an East Asian country came forward with information about a series of planned terrorist attacks 48 hours before they took place. Authorities were able to foil the plot and the tipster and his family was relocated.

In another case, a woman studying at a foreign university witnessed an attack on a U.S. diplomat. The information she provided led to two of the attackers receiving life sentences. The tipster and her family were also relocated, according to the State Department.

While the identity of tipsters typically remains confidential, there have been four public reward ceremonies in the Philippines, with the latest one occurring on June 7, 2007. The combined reward amounts for those ceremonies reached $10 million, according to the State Department.

Other big successes for the program include the deaths of Uday and Qusay Hussein – the sons of former Iraqi President Saddam Hussein. On July 23, 2003, information provided by a tipster led to the location of both brothers and their eventual deaths. It was the largest payment to date for the program -- $30 million.

Confirmation that a reward had been offered for information on the Benghazi attack came out of a congressional inquiry by House Homeland Security Chairman Rep. Michael McCaul.

The Texas Republican sent a letter to Secretary of State John Kerry asking why the government wasn’t using its RFJ program to help catch the killers behind the attack in Benghazi on Sept. 11, 2012, which led to the deaths of four Americans, including U.S. Ambassador Chris Stevens.

The letter from McCaul, which had 84 co-signers, including the chairman of the Foreign Affairs and Armed Services Committees, pressed the State Department on its lack of action.

“It is hard to understand why the State Department, which describes the Rewards for Justice Program as one of the most valuable assets the government has in fighting terrorism, has failed to use it to help apprehend the terrorists who committed this act,” the letter said. “If catching these terrorists truly is a top priority for the State Department then Secretary Kerry will act immediately and begin using this program today.”

As a result of the inquiry, it was released that the government had been offering a reward for Benghazi since January. The State Department defends its decision to keep the reward under wraps, although it would not say why the reward was not publicly advertised on the RFJ website.

“Benghazi stands out an as exception to the usual procedure,” Kevin Shipp, a former Central Intelligence Agency officer, told FoxNews.com. “The Department of State has gone to great lengths to ensure this information does not become public and refused to reveal the names, if any, placed on the list.”

The RFJ program was started in 1984 and based in the Department of State’s Bureau of Diplomatic Security.

A group of private citizens approached the State Department after the Sept. 11, 2001 attacks and sought approval to raise additional reward money through donations from the general public to support RFJ. The fund was then set up as a non-governmental, non-profit 501(c)(3) charitable organization. The public fund, though, was disbanded in August 2008.

The program got a boost via the 2001 Patriot Act, which widened the scope of the program. It also significantly upped the payouts. The reward for information leading to the capture of Usama bin Laden, for example, was raised to $25 million.

The reward amount is based on the threat posed by a suspect.

Still on the lam are people like Abubakar Shekau, the leader of Jama’atu Ahl as-Sunnah il-Da’awati wal-Jihad -- which also goes by the name Boko Haram. The State Department is offering up to $7 million for information on Shekau, who is accused of trying to overthrow the current Nigerian government and replace it with one centered on Islamic law.

Another terror leader on the loose is Mokhtar Belmokhtar, the founder of the Signed-in-Blood Battalion and a leader with a prominent Al Qaeda affiliate. The reward on him is up to $5 million.

While successful strikes and raids using information from the RFJ program have brought down criminals abroad, there have been some growing pains and tactical head-scratchers.

During the hunt for bin Laden in 2002, U.S. planes dropped matchbooks with the Al Qaida terrorist’s face on them. The matchbooks explained in the local language that authorities were looking for the terror leader and that there was a reward tied to his capture. There were instructions to go on the RFJ website and an email address, which was mostly met with puzzlement by people who came across the matchbooks. Under the Taliban regime, there had been a ban on computers and therefore access to them was limited at best.

Another complication of monetary rewards is the possibility of false information or leads, some say. Still, others say it’s worth it.

“The real possibility of being fed false information has always been a challenge for the program, similar to the FBI’s (Most Wanted) list,” Shipp said. “Both programs have mechanisms to vet and eliminate information that may be unreliable. The same would apply to the television program ‘America’s Most Wanted.’ All these programs face this challenge, but the gains have always outweighed the risks.”