The deadly attack this week on a satirical newspaper in Paris illustrates an increasing challenge for intelligence officials from "lone wolf" suspects, according to National Security Agency (NSA) Director Adm. Michael Rogers.

While terrorist plots in the wake of 9/11 were complex and involved, recent attacks have been carried out by individual perpetrators who "use targeted violence or indiscriminate violence as the vehicle to help perpetuate" their viewpoint on others, Rogers said, mentioning the 2013 Boston bombing.

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"That's not a good development for us. That certainly increases the challenge from an intelligence perspective," Rogers said in an interview with the Fox Business Network posted Friday.

"Boy, that makes life a whole lot harder," he added.

French police on Friday killed two brothers suspected of shooting dead a dozen people at the offices of the Charlie Hebdo satirical newspaper in Paris earlier this week. A third suspect, 18 years old, turned himself into authorities shortly after the attack Wednesday.

The brothers, both French citizens in their 30s, had previous terrorist involvement.

American officials said the older of the pair, Saïd Kouachi, trained with al Qaeda's affiliate in Yemen before returning to France, according to The New York Times. Chérif Kouachi was a pizza deliveryman previously arrested for involvement with a Parisian terrorist recruitment cell.

The men allegedly shot up the newspaper offices and fled before authorities arrived, leading to a massive two-day manhunt. The outlet had previously been targeted for its caricatures of the Prophet Muhammad.

Michael Hayden, a former director of both the NSA and CIA, said Thursday on NBC's "Today" show that the Paris assault illustrates "the high end of the new genre of attacks," suggesting terrorists are targeting smaller targets using quicker plots.

"I was talking to you guys about 12 months ago about these massive amounts of metadata the NSA held in storage. That metadata doesn't look all that scary this morning," Hayden said Thursday on MSNBC's "Morning Joe."

"I wouldn't be surprised if the French services pick up cellphones associated with the attack and ask the Americans — where have you seen these phones active globally?" he added.

Rogers, when discussing the transparency of his agency, emphasized the need to discuss intelligence-gathering tactics in broad terms to avoid tipping off potential targets but noted the agency's efforts "to attempt to forestall some of these events like we've seen in Paris."

In an interview set to air on "Fox News Sunday," Gen. Martin Dempsey, chairman of the Joint Chiefs of Staff, said the Parisian attackers had external influence.

“These individuals were inspired in some way. They didn’t, they probably were not self-radicalized on the Internet, which is another way that these attacks sometimes occur," Dempsey said.

"There is pretty clear indication that at least one of them did receive some training in Yemen. And that there’s a linkage among them, whether it’s schools or family relationships. As far as whether it was directed by al Qaeda, I don’t think that linkage has been established," he added.