In May 2007, al-Qaida released an interview with one of its leaders in Afghanistan.
The interviewer asks, "What are the needs of jihad in Afghanistan?" In the video, provided by the Middle East Media Research Institute, Sheik Saeed replies that the first need is financial. He goes on in Arabic, "There are hundreds wishing to carry out martyrdom-seeking operations, but they can't find the funds to equip themselves. So funding is the mainstay of jihad."
To people who fight terrorist financing, that video is proof of success.
As President Obama changes course on many national security policies, he has indicated that he plans to stay on the path charted by the Bush administration when it comes to tracking terrorists' money.
In January, he asked the Treasury Department's undersecretary for terrorism and financial intelligence, Stuart Levey, to remain on the job.
On Wednesday morning, a congressional committee will hold a hearing about a recent terrorism finance tracking program that teams up Treasury and Defense department officials.
Matthew Levitt used to work on terrorism financing at the Treasury Department. He recently authored a report for the Washington Institute for Near East Policy, called "The Money Trail."
"If terrorists need money to do something, even if they only need a little bit of money but they can't get that money where and when they need it, you can have an extremely disruptive effect on their efforts to carry out attacks," Levitt says.
Broadly speaking, the U.S. has two ways to go after terrorist financing. Officials can start with a known bad guy and follow the money trail, or they can sift through millions of financial transactions looking for something suspicious.
The first model is not very controversial. In fact, many people are excited about a recent program that gives soldiers tools to follow terrorists' money.
"Soldiers in Afghanistan have been supplied with card readers. And that wouldn't have happened five or six years ago," says Andrew Cochran, founder and co-editor of the Counterterrorism Blog.
A soldier can scan a credit card found at the scene of a military raid. It might tell him who is in a terrorist financial network and how much money is in the account.
"When you think back to American wars, military action in the past from Desert Storm, Vietnam, Korea, World War II, we didn't do that kind of thing," says Cochran. "There wasn't that kind of effort to determine the financing of Viet Cong guerrillas."
The second model of tracking terrorist money starts with financial institutions like banks. The banks give the FBI information about suspicious-looking transactions, and the FBI decides whether to follow up. Government officials defend this program, but not everyone is convinced it works.
Mike German spent 16 years at the FBI and now works for the American Civil Liberties Union.
"Show me the evidence. Don't tell me an anecdotal story. Even a blind squirrel finds a nut sometimes," says German. "If you look at the data, what you see is this enormous increase in surveillance with a really startling drop-off in prosecutions."
Even people who support financial surveillance say it's hard to prove the program's effectiveness by looking at public data.
"I admit I've been out of government two years now," says former Treasury official Levitt. "I've been trying to come up with useful metrics to measure this, and I've failed miserably. So where we still are left today, and it's insufficient, is the periodic declassified anecdotes."
For example, the U.S. says it caught the mastermind of the attacks on Bali by tracing money. The British say they thwarted a bomb plot at Heathrow by tracking finances.
Dennis Lormel created the FBI's terrorist financing operations section after Sept. 11, and he now works for a consulting firm called IPSA International. He is convinced that the FBI's operations on this front have made a major impact on global terrorism, but he wishes there were better public statistics to show for it.
"It's one of the areas that is a rub," says Lormel. "The government needs to do a better job providing feedback mechanisms that demonstrate the value of the information."
After Sept. 11, banks spent a fortune to comply with laws like the USA Patriot Act. They hired outside consultants to make sure the banks reported every suspicious transaction. Since the economy went bad, banks have been laying those people off. Now Lormel is worried that terrorists will use that opportunity.
"You can rest assured that they're looking to adapt and be able to exploit new vulnerabilities," says Lormel. "Unfortunately, those new vulnerabilities are going to be out there. It's a troubling time, and it's a really scary time."