New York: The arrest of naturalised American Faisal Shahzad for the failed Times Square bomb scare has hightlighted yet again a trend that experts say poses the biggest challenge America's security officials have ever faced.
When war veteran Timothy McVeigh bombed a federal building in Oklahoma City in 1995, killing 168 people, the US was stunned.
Since then, there have been many such cases of home grown terror.
In November 2009, Army Major Nidal Malik Hasan killed 13 and injured 43 in a shooting rampage at Fort Hood in Texas.
In December 2009, the FBI charged US citizen David Coleman Headley with conspiring with the Lashkar-e-Taiba, to plan the Mumbai attacks.
Again in December, five American muslims from Virginia were captured in Pakistan attempting to join the Taliban.
Britain is not immune to this phenomenon either.
A Nigerian muslim Umar Farouk Abdulmutallab who tried to blow up a plane heading to Detroit in December was believed to have got radicalised at University College London (UCL). Other incidents where Pakistani students were arrested on charges of trying to plot terrorist attacks which is why recently CIA asked intel agencies in London to give them files with details of 1,000 British muslim students.
On July 7, bombings on London's transport system were carried out by four Muslim men, three of them British Pakistani and one of British Jamaican descent, who were motivated by Britain's involvement in the Iraq War.
And the recent arrest of Faisal Shahzad, the failed Times Square bomber has only underscored the huge challenge security officials now face - that of-home grown terrorism.