The latest target for armed civilians patrolling US-Mexico border? Terrorists.

For years, volunteer groups of armed civilians have patrolled the US-Mexico border in a personal crusade against illegal immigration, drug smuggling, and human trafficking.

Now, in the wake of the Paris terror attacks, some of these civilian patrols are turning their focus to another threat: terrorists trying to slip through the southern border.

“We have pictures from trail cameras that show Somalis and Middle Eastern guys with beards and everything else, but nobody is listening,” Tim Foley, Field Operations Director of Arizona Border Recon, told The Washington Post last week. “We’re going to have something like Paris had. It’s not a matter of if, but when.”

His group is comprised of former veterans, law enforcement, and private security experts, as well as civilians, who voluntarily monitor parts of the US-Mexico border for illegal immigrants and now, terrorists. Arizona Border Recon and groups like it have raised concerns about vigilantism and questions about the link between immigration and terrorism, as well as applause from some quarters for its service and initiative.

“Everything’s coming across this border. Dope, disease, scumbags, terrorists...(and the government is) not doing what it’s supposed to be doing — protecting our country,” Mr. Foley told Al-Jazeera America for an Oct. 2014 article.

Foley's group is a citizen effort to fix a perceived gap in US border security.

"We are not affiliated with any form of government, nor are we a militia. Our objective is not to overthrow any government, or take the law into our own hands. We are not here to replace the Border Patrol. We operate within the scope of the law as citizens, by observing and reporting what we see," the group's website states.

If they encounter suspected illegal immigrants, the group's volunteers detain them, search for weapons, and check them for medical needs while calling Border Patrol to make an arrest, according to the group's procedures.

Over the course of almost five years, Arizona Border Recon has detained hundreds of people, including illegal immigrants and drug mules.

Its new focus on finding terrorists has once again raised questions on the link between immigration and terrorism.

The Paris terror attacks ignited an anti-immigrant and anti-refugee wave across much of the Untied States. In the wake of the attacks, more than half of US governors have now issued statements saying they would reject Syrian refugees.

Almost every Republican presidential candidate has now made calls to end all Syrian refugee arrivals, or to accept only Christian, not Muslim, refugees. And a Reuters/Ipsos poll conducted after the attacks found that 52 percent of Americans think that countries accepting Syrian refugees are "less safe."

This, despite evidence that the Paris terror attacks appear to have been carried out by citizens of European Union countries, not smuggled terrorists, according to investigations.

Nonetheless, officials have suggested the threat of terrorists sneaking in through America's southern border is real. On Nov. 19, the FBI confirmed that five men from Pakistan and one from Afghanistan were captured near Arizona’s border with Mexico.

"This latest incident only reinforces the need to take our national security seriously on all fronts," Ariz. Gov. Doug Ducey said in a statement. "It's clear, our nation needs to up its game and improve border resources if we are going to protect our homeland."

Still, even as it steps up to respond to threat like this, Arizona Border Recon has raised concerns of clashes with law enforcement and of vigilantism.

US Customs and Border Protection, which oversees the Border Patrol, released a statement that it “appreciates the efforts of concerned citizens as they act as our eyes and ears” but “does not endorse or support any private group or organization from taking matters into their own hands as it could have disastrous, personal and public safety consequence[s].”

Despite this, reports suggest the Arizona Border Recon group has a close working relationship with the Border Patrol, with volunteers regularly sharing information with Border Patrol agents.

And while some groups, such as the Southern Poverty Law Center, have described the group as "nativist extremists," Foley says his group is not against immigration and simply wants to keep the country safe.

"We're not against immigration, we just want it done the right way, because your friends wouldn't climb through the back window to come visit you. If you come through the front door that's fine, but we don't know who's who," he told Fox News.

"If getting off the couch and doing something to protect your country is extreme, then yeah, I guess you can call us extremists."