A report released Monday by the Congressional Research Service (CRS) finds that homegrown terrorist plots have risen sharply since 2009, suggesting that some Americans "are susceptible to ideologies supporting a violent form of jihad."
"CRS estimates that, since May 2009, arrests have been made in 50 homegrown jihadist terrorist plots by American citizens or legal permanent residents of the United States as part of a much discussed apparent uptick in terrorist activity in the United States," the report states.
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The number of homegrown plots is more than twice what it was in the years following 9/11.
"In more than seven years from the September 11, 2001, terrorist strikes (9/11) through May 2009, there were 21 such plots," the CRS said. "Two resulted in attacks, and never more than six occurred in a single year (2006)."
"The apparent spike in such activity after May 2009 suggests that at least some Americans—even if a tiny minority—are susceptible to ideologies supporting a violent form of jihad," the report said. "Most of the homegrown plots after May 2009 likely reflect a trend in jihadist terrorist activity away from schemes directed by core members of significant terrorist groups such as al Qaeda."
Three plots since 2009 have resulted in attacks, including the Boston Marathon bombing this year, the attack on Fort Hood by Maj. Nidal Hasan, and a shooting at the U.S. Army-Navy Career Center in Little Rock, Ark., by Abdulhakim Muhammad.
The CRS defines homegrown as "terrorist activity or plots perpetrated within the United States or abroad by American citizens, legal permanent residents, or visitors radicalized largely within the United States."
Additionally, reports indicated that several of the militants behind the terrorist attack on a Kenyan mall last weekend, which killed more than 60 people, were American teenagers.
Al Shabaab, the al Qaeda aligned terrorist group responsible for the attack, has been active in recruiting Americans, mainly in the Minneapolis area.
According to the report, "lone wolves" have proven to be the most successful in attacking the United States since 9/11, and support for jihad comes in a variety of forms.
"Some individuals focused on becoming foreign fighters in conflict zones, such as Somalia," the report said. "Others planned attacks using explosives, incendiary devices, or firearms. Yet others incorporated multiple, unspecific, or unique tactics. Finally, outside of the post-9/11 violent plots, additional individuals intended only to fund or materially support jihadist activities."
The report also found that law enforcement has been successful in foiling plots using the "‘Al Capone’ approach," where suspected terrorists are arrested for violations of civil laws unrelated to their terrorist activity, and undercover operatives.
"These tactics have long been used in a wide variety of criminal cases but have particular utility in counterterrorism investigations as they allow suspects to be arrested prior to the commission of a terrorist act rather than after the damage has been done," the CRS said.