Dzhokhar Tsarnaev, one of two terrorists responsible for the bombing carried out at the Boston Marathon this yearCorbis Images

After his capture by Boston police and federal agents, Dzhokhar Tsarnaev during his interrogation with FBI agents confessed that he and his brother, Tamerlan, had selected New York as a target to carry out their next attack. The brothers had intended to detonate explosives at Times Square.

Given that the brothers' actions killed three people and injured 264 others in Boston, had the two carried out their plan in New York, there is little doubt that the planned attack would have led to further casualties. If the brothers weren't stopped in Boston, who knows how much more damage they could have done?

The tragedy in Boston came as a shock given how long it has been since there has been a major attack in the United States. Since Sept. 11, 2001, there have been dozens of failed terror plots targeting U.S. soil, foiled often by law enforcement authorities and occasionally by sheer luck.

Quazi Mohammad Rezwanul Ahsan Nafis intended to detonate a massive bomb, though he never had the means to do so.Corbis Images

Last year, Quazi Mohammad Rezwanul Ahsan Nafis, a 21-year-old Bangladeshi man, attempted to detonate what he believed to be a 1,000-pound bomb outside the Federal Reserve Bank of New York building. The device he used in the attack was in fact inert and supplied by law enforcement as part of an elaborate investigation, according to CNN.

Although Nafis was motivated by al Qaeda terror propaganda, whether he had any ties to the organization isn't clear. Nafis plead guilty to the charge of attempting to use a weapon of mass destruction, and faces life imprisonment at his sentencing on May 30.

Police clear the area around which the Times Square bomber in 2010 intended to detonate a car bomb.Corbis Images

The Tsarnaev brothers weren't the first terrorists to target Times Square and fail. In 2010, a crude car bomb place in an abandoned Nissan Pathfinder prompted the evacuation of thousands of people over what turned out to be an unsuccessful terror plot.

The bomber, Faisal Shahzad, a Pakistani-born American, was arrested and charged with multiple counts on terrorism-related charges. During his trial, Shahzad showed no remorse for his actions, and was sentenced to life in prison without the possibility of parole.

After the attempt by underwear bomber, airport security began using backscatter X-ray machines.Corbis Images

Some terror plots are foiled simply by sheer luck.

During Christmas 2009, Umar Farouk Abdulmutallab, now infamous as the underwear bomber, nearly succeeded in his plot to detonate plastic explosive he had concealed in his underwear aboard a flight from Amsterdam's Schipol airport to Detroit, Michigan.

Trained and equipped by al Qaeda, Abdulmutallab claimed at his trial that he was "proud to kill in the name of God." Abdulmutallab received multiple life sentences for the attempted attack.

Abdul Kadir, one of the JFK airport bomb plotters, is led out of court.Corbis Images

In 2007, Islamist terrorists targeted another major New York City landmark, John F. Kennedy airport. A group of four men, three from Guyana and one from Trinidad and Tobago, had targeted airplane fuel tanks and pipelines to carry out an explosive attack.

According to officials and documents released on the case, the plotters didn't have any ties to al Qaeda or other prominent terror groups, and their operation hadn't gone beyond the planning stages.

Terrorists targeted planes leaving London's Heathrow airport.Corbis Images

In 2006, 24 suicide bombers planned to pack their carry-on luggage full of liquid explosives, carry them on flights bound from London to the United States and use them mid-flight. According to U.S. officials, the explosives were made of a peroxide-based solution that had to be assembled on-board and could detonate them with just about any simple portable electronic device, as reported by NPR.

An operation led by British police over several months led to the capture of the terrorists a mere two weeks before they planned on executing their plot.

High value targets like the New York Stock Exchange can attract the attention of terrorists.Corbis Images

In 2004, Dhiren Barot, a British al Qaeda operative, plotted to bomb the New York Stock Exchange, the World Bank and several high-end hotels in London, among other targets. Barot's plan was to leave limousines packed with explosives in the underground garages of these buildings to carry out his attack. Barot also had plans to fabricate a so-called "dirty bomb," an explosive that contains radioactive material.

Barot was sentenced to life in prison for his plans to commit mass murder.

Iyman Faris proved to be useful to investigators after confessing to a bomb plot.Corbis Images

In 2003, an al Qaeda operative, Ohio trucker Iyman Faris, a Pakistani-born American, intended to bring down Brooklyn Bridge. Faris received special training on making explosives specifically for suspension bridges, according to an Egyptian detainee named Tariq Mahmoud Ahmed al Sawah during an interrogation with U.S. intelligence.

Upon receiving a visit from the FBI over his contacts with al Qaeda, Faris confessed to the plot, and cooperated with investigators. At his trial that same year, Faris was sentenced to 20 years in prison.

Anytime you have to take your shoes off in a security line at the airport, remember that this man, Richard Reid, is the reason why.Corbis Images

Sometimes terror plots can be disrupted by the very people that might otherwise have been victims.

In 2001, just three months after the attacks of September 11, Richard Reid, an al-Qaeda-trained British citizen, boarded American Airlines flight 63 from Paris to Miami and attempted to detonate a shoe packed with explosive materials. Noticing his unusual behavior, passengers subdued Reid before he could succeed, and the plane landed safely at Boston's Logan airport.

Reid was sentenced to life in prison without the possibility of parole in 2002, and is serving his time in a federal supermax facility.