America must be, and is, ever vigilant in the war against terrorism — whether from the Islamic State group recruiting sympathizers in Iraq or bigoted extremists fomenting violence in Virginia, the nation’s second highest-ranking prosecutor said Wednesday.

“We must never let down our guard, because our enemies do not fight fair,” Deputy U.S. Attorney General Rod Rosenstein told Utah law enforcement personnel. “Terrorists are cowards who target unsuspecting people going about their lives — watching a soccer game, dancing at a nightclub, traveling to work, walking down a street.”

Rosenstein made his comments at the Utah National Security and Anti-Terrorism Conference, held at the Sheraton Hotel in downtown Salt Lake City. About 600 people from local, state and federal law-enforcement agencies attended the two-day gathering, which began Tuesday.

Some of the most powerful tools to confront terrorists are Joint Terrorism Task Forces and fusion centers — including Utah’s Statewide Information and Analysis Center — that share intelligence about threats, Rosenstein said.

“If we want to prevent attacks, we need to be vigilant,” he said. “We know the key is to collect all available information and generate actionable intelligence to disrupt terrorists before they strike.”

Since the 9/11 attacks, law enforcement has met with success by working with the intelligence community to disrupt dozens of terrorist threats, Rosenstein said. He also noted that the number of Americans trying to travel to join the Islamic State has “dropped significantly,” from six to 10 a month a few years ago to often one or none now.

Much of the credit for that ”positive development” goes to the military, which has fought ISIS on the battlefield, and to local law enforcement officers for their “proactive policing,” Rosenstein said. In recent years, the Justice Department has filed terrorism-related charges against more than 145 foreign fighters, homegrown extremists and ISIS supporters, he said, and the FBI has ongoing investigations in all 50 states.

“A word of caution is in order: Some people who would have left America now pose a danger here instead,” he warned. “ ... Returning foreign fighters can present significant security risks because of their ideology, combat training and connections to terrorist networks.”

The Justice Department also remains vigilant about the threat of violent domestic extremists, who often are motivated by hatred and bigotry, Rosenstein said. He cited, for example, an alleged plot last year targeting an apartment complex in Garden City, Kan., where Somali immigrants live.

Rosenstein noted the white nationalist demonstration that turned violent and deadly a few weeks ago in Charlottesville, Va., “where we saw and heard people openly advocate racism and bigotry.” He said the Justice Department is working with local authorities on potential civil rights prosecutions.

“The First Amendment often protects hateful speech that is abhorrent to American values,” Rosenstein said. “But there can be no safe harbor for violence.”

He pointed out that U.S.-based extremists have plotted attacks on government buildings, businesses and houses of worship.

”They have planned and carried out assassinations of police officers, judges, doctors and civil rights leaders,” he said. “They have acquired biological and chemical weapons, illegal firearms and explosives.“

Rosenstein also said:

• Violent domestic extremists pose a particular danger to law enforcement officers because some target police. Examples include tragedies in Las Vegas, Dallas and New York.

• A growing challenge is the use of encrypted communication channels by terrorists groups, making it harder to to learn about planned attacks.

• Having a critical incident response plan in place ahead of an attack is important to avoid duplication and to coordinate efforts among agencies.

After his remarks, Rosenstein joined U.S. Attorney for Utah John Huber at a news conference in which they announced that battling violent crime will be a top priority of federal prosecutors.

Huber said that while violent crime has risen in the nation by about 3 percent to 5 percent, Utah has seen a 13 percent jump. He pointed out there were 19 drive-by shootings in Salt Lake County in 2015 and 89 in 2016.

In response to the spike, Huber said, he has reorganized his office to work with local law enforcement, targeting crimes such as narcotics trafficking, gang activity, robberies and gun violations.