Around Thanksgiving time last year, the FBI and NYPD suddenly warned of a terrorist threat against the commuter rail lines in the New York metro area. Security was stepped up. There was the usual round of reporting on whether or not the threat was legitimate. And then the story died. That is, the story was dead until last week.

Press reports published in the past week indicate that the source of the threat spike was intelligence gleaned from the FBI's interrogations of a Long Island man named Bryant Neal Vinas. His story is equally troubling and fascinating. The most troubling aspect of Vinas's tale is that he was sitting in a mosque in eastern New York when he decided to travel thousands of miles abroad to join al Qaeda and the Taliban. Thus, Vinas joined the ranks of hundreds of other so-called "homegrown" jihadists who were inspired to wage jihad while living in the West. Vinas's story is also fascinating because he managed to meet with and serve senior al Qaeda and Taliban terrorists in Pakistan in a relatively short period of time. His access to senior al Qaeda leaders was so good that he has reportedly become a valuable informant.

We are left to ask: How did Vinas manage to gain the trust of some of the most dangerous and paranoid terrorists on the planet?

Court documents released online tell Vinas's story. In January of this year, Vinas confessed to a Brooklyn court (transcript available at intelwire.com):

In the fall of 2007, I left my home in Long Island to travel to Pakistan with the intention of meeting and joining a jihadist group to fight American soldiers in Afghanistan. When I arrived in Pakistan, I made contact with and was accepted into al Qaeda, a jihadist group that I knew to be responsible for attacks against the United States, including suicide bombings targeting civilians.

As a member of al Qaeda, I received training in courses in general combat and explosives. During my time in al Qaeda, I took part, at the direction of al Qaeda leaders, in two missions in September 2008 in which we agreed and planned to attack a United States military base near the border of Pakistan and Afghanistan. The first attack failed and we had to abort the mission before firing on the base, but a few days later, I took part in firing rockets at an American military base. Although we intended to hit the military base and kill American soldiers, I was informed that the rockets missed and the attack failed.

Finally, during my time with al Qaeda, I consulted with a senior al Qaeda leader and provided detailed information about the operation of the Long Island Rail Road system which I knew because I had ridden the railroad on many occasions. The purpose of providing this information was to help plan a bomb attack of the Long Island Rail Road system.

What Vinas did not reveal in his confession is how, precisely, he came to make "contact with" and be "accepted into al Qaeda." This is no small feat. For years, western intelligence services, which have reportedly had little success infiltrating al Qaeda's ranks, have complained that al Qaeda's measures keep them out. Al Qaeda has strict security protocols to prevent spies and saboteurs from entering its ranks. For example, al Qaeda members are frequently required to vouch for new recruits. If the new recruit turns out to be an "unfriendly," then al Qaeda knows who let him into their club. This acts both as a deterrent (no one wants to vouch for a rat and, therefore, suffer the consequences), as well as an easy-to-employ counterintelligence tactic. The result is, with few exceptions, only the most committed jihadists are let into al Qaeda's clubhouse.

Vinas managed to assuage any of al Qaeda's and the Taliban's security concerns rather quickly.