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The self proclaimed Islamic State (ISIS) has been tied to at least 75 terrorism plots against Western countries, with the United States as the group’s main target, according to a recent report by the House Committee on Homeland Security.

The Committee’s report, “Terrorism Gone Viral,” revealed a significant increase in terrorist plots against the West over the past several years. In 2014 there were 19 ISIS-linked plots against the West; in 2015, the figure more than doubled to 48. The high success rate—with more than 40 percent of total plots executed—indicates that the group will likely continue to initiate frequent attacks, versus long-term plots. More than one-third of ISIS-linked terror plots were aimed at the United States or its interests overseas. These plots included the tragic San Bernardino shooting in December 2015, which killed 14 and injured many more; an attempted ISIS-inspired attack in Garland, Texas; numerous attempts to attack New York City landmarks; and many others.

According to Homeland Security Today, ISIS-inspired attacks targeting the West are not only growing in number, they are getting deadlier. In the second half of 2014, an average of one individual died in each successful attack, compared to the first half of 2015, which saw the average death toll rise to 11.

The report also noted that US officials are growing increasingly concerned that terrorists are “going dark”—the public safety problem created by failure of law enforcement to keep pace with technology—making it increasingly difficult to mitigate attacks. A number of high-profile terrorism cases have involved ISIS-linked attackers encrypting their communications or making their data inaccessible to authorities, including in Garland and Paris. In the Garland case, the suspect reportedly exchanged 109 encrypted messages with a known terrorist overseas before his attack, and in the Paris case, the attackers allegedly used encrypted communications in advance of their operation.

Another alarming trend is that the line between inspired and directed plots is getting blurrier. For example, an individual can start off self-radicalized and later gain ties with ISIS. Many lone-wolf actors are not actually acting alone and are later discovered to be linked to ISIS operatives overseas.