"They have the capability and the intent. All they're lacking is the catalyst. And there lies the problem," he explained, adding he believes the government needs to look closer at whether a group is on a trajectory to violence.
Any counterterrorism efforts should be proactive rather than reactive. But Johnson claims the current approach is a hands-off one unless the group is engaging in some criminal activity.
"These groups proliferate like mushrooms after the spring rain," he said. "Criminal activity will certainly follow."
He explained that the election of President Barack Obama has been a huge factor in the proliferation of extremist groups at home.
"It's their worst nightmare come true," he said.
The election of the first black president sent shockwaves through many of these right-wing groups who feel threatened by the changing demographics of the nation. Johnson predicts that if Obama wins a second term, there will be more violent attacks by these domestic groups.
Yet there remain massive gaps in domestic counterterrorism efforts, according to Johnson.
Following a 2009 Department of Homeland Security report authored by Johnson on the growing threat posed by right-wing extremist groups, the domestic terrorism unit under the DHS was disbanded because of pressure from the political right-wing, claims Johnson.
Conservative media political analysts like Michelle Malkin, Sean Hannity, Lou Dobbs and Rush Limbaugh criticized the report as an attempt to demonize the right. It also drew criticism from some members of the military because the report claimed right-wing extremist groups recruited veterans and soldiers.
After the release of the report, a number of draft reports were put on hold or canceled entirely,according to Johnson. Products that concerned domestic terror were subject to greater scrutiny and stalled in an effort to kill the work, said Johnson.
"These restrictions were selectively applied to work on domestic terrorism than to jihadi terrorism," he said, adding that his frustration led him to quit a year later.
Resources devoted to domestic counterterrorism have been cut, and there is now only one intelligence analyst at the DHS looking at domestic terrorism. That's compared to five after 9/11, according to Johnson.
There is also a void in training officials to recognize these threats, Johnson claims. While the DHS has implemented some training in the last year -- nine sessions so far -- they have not been sufficient, Johnson explained.
In his time there, the DHS ran up to 10 sessions per month. Training sessions by other agencies remain limited in scope, Johnson explained. The FBI, for example, focuses mainly on the sovereign citizens groups, he said.
In a 2008 meeting between the counterterrorism units of the FBI and DHS, it was apparent the FBI did not have the proper information to investigate, according to Johnson.
"They didn't even appear aware of the resurgence of militias and extremist groups," Johnson said.
DHS spokesman Peter Boogaard said he could not comment on these assertions as they involve classified information. But in a written statement he said the DHS "protects our country from all threats, whether foreign or homegrown, and we know that violent extremism is neither constrained by international borders, nor limited to any single ideology.
"As such, DHS continues to work with its state, local, tribal and territorial partners to prevent violence that is motivated by any extreme ideological beliefs. This includes training law enforcement to recognize behaviors and other indicators associated with violent criminal activity as well as briefings, products, case studies, and information sharing on violent extremist threats," the statement said.
In an April 2005 report titled "10 Years After the Oklahoma City Bombing: the Department of Homeland Security Must Do More to Fight Right-Wing Terrorists," Rep. Bennie Thompson, then-head of the House Committee on Homeland Security, called for a renewed effort to catalog the risks posed by right-wing domestic terrorists. In the report, he slammed the DHS for omitting the threat of right-wing terror threats in a long-range planning document.
"Democratic members of the House Committee on Homeland Security are very concerned that this oversight demonstrates DHS administrators are not adequately considering right-wing domestic terrorist groups that are focused on attacking America in order to further their political beliefs," he wrote.
The government is also inconsistent in how it categorizes domestic extremist groups. While the federal government lists groups such as al Qaeda and Hezbollah as terrorist organizations, there is no such practice of designating any domestic groups as terrorist organizations.
According to the State Department's Bureau of Counterterrorism, the secretary of state had designated 49 foreign terrorist organizations as of January 2012. The FBI and Department of Justice do not generate an official list of domestic terrorist organizations.
The lack of such a list may make it difficult to assess the scope of domestic terrorism and evaluate trends and counterterrorism efforts. It also creates the misconception that terrorism comes only from abroad.
However, advocacy groups like the American Civil Liberties Union object to such categorizations, arguing that labeling some domestic groups as such would discourage free speech and expression.
Michael German, an expert at the ACLU who has also worked as an FBI agent for 16 years, argued that any characterization of groups that are not engaged in criminal activity is problematic.