(NewsNation) — Recent attacks in Europe are putting a spotlight on the sort of terrorism threats that U.S. officials have been warning about.

Most recently, two suspects, apparently inspired by the Islamic State group and al-Qaida, were arrested in connection to an apparent plot to attack Taylor Swift shows in Vienna, Austria. Three sold-out concerts were canceled in response.

An attack in March that the Islamic State claimed responsibility for, in which several assailants burst into a large concert hall in Moscow, Russia and opened fire, also set officials on alert. At least 143 deaths were reported, and more than 100 people were injured.

The Terrorism Research & Analysis Consortium tells NewsNation threats like these have escalated significantly over the past one to two years. For the United States, the biggest risks are lone wolf or small group attacks inspired by ISIS, the organization said.

Retired Col. Myles B. Caggins III of the New Lines Institute used to be the spokesman for the global coalition to defeat the terror group.

“We see from the threats to the Taylor Swift concert that ISIS wants to conduct attacks for an information win,” Caggins said in an interview. “If there is an attack that ISIS terrorists do that’s spectacular, it’s more likely to inspire recruits to join their evil cause. So Americans must remain vigilant as individuals and law enforcement and intelligence must continue to cooperate to share information, to disrupt and capture and arrest any potential terrorist.”

National security concerns

FBI Director Christopher Wray warned of an increased national security threat while testifying at a hearing before Congress in April.

“As I look back over my career in law enforcement, I would be hard-pressed to think of a time where so many threats to our public safety and national security were so elevated all at once,” Wray said then.

Just in the last month, according to a report by the United Nations Security Council, the Islamic State in Iraq and the Levant have used recent attacks in Europe, Africa and othe regions “to support an enhanced propaganda effort to heighten public perceptions of threat in order to recruit new members.”

Vladimir Voronkov, the UN’s undersecretary for counterterrorism, told members that IS group affiliates have “expanded and consolidated their area of operations” in West Africa and the Sahel, the area between equitorial Africa and the Sahara Desert.

IS group affiliates have also expanded operations in other parts of the continent, including parts of Mozambique, Somalia and the Democratic Republic of the Congo, which saw a “dramatic increase in terrorist attacks” that killed large numbers of civilians.

The Associated Press contributed to this article.