Counter-terrorism officials look for ways to stop small unmanned aircraft.

Two hand-launched unmanned aerial vehicles made headlines at about the same time earlier this year.

On Feb. 2, a DJI Phantom quad-copter crashed on the White House lawn. The incident sent Secret Service agents scrambling.

About one week prior to that incident, a small UAV with sixpropellers crashed in a Tijuana, Mexico, hotel parking lot a short distance from the border with San Ysidro, California. Aboard was three kilograms of narcotics, local news reported.

"All of the sudden everyone is screaming about counter-UAVs," said Robert Newberry, director of the Combating Terrorism Technical Support Office.

The CTTSO is responsible for developing new technologies to solve tough problems facing law enforcement and counterterrorism professionals.

The two incidents have put a spotlight on the counter-UAV problem, Newberry said at the National Defense Industrial Association's Special Operations/Low Intensity Conflict symposium.

The White House incident turned out to be an accident. A drone user in a nearby apartment lost control of the toy. But it did highlight a potential vulnerability.

As for the incident at the border, the intentions were fairly obvious, he said.

"I don't think they are using quadcopters to move heroin in Tijuana. I assume it was to come across the border," he said.

The Islamic State terrorist group is employing drones. And New York City police are reporting that peeping toms are using them to peer into residents' windows, he noted.

The CTTSO is looking...