As Canada’s military prepares to engage the Islamic State terrorist group ISIS overseas, the battle has taken another turn closer to home, where threats have been leveled and security agents recently detailed the task they faced in monitoring as many as 80 suspects currently on Canadian soil.

The head of the Canadian Security Intelligence Service (CSIS) recently confirmed the number of people who have returned to Canada after visiting violent regions around the world. According to QMI Agency, Michel Coulombe said the spy agency knows exactly where each of those suspects is.

Coulombe further added there were more Canadians, between 130 and 145, currently overseas and involved with terrorist groups. The news comes on the heels of a compelling report from NBC News, which cites intelligence officials who say Canadian authorities have overheard terrorist suspects plan ISIS-inspired attacks inside the country.

The report, which underlines the realities of the threat of the Islamic State (often referred to as ISIS or ISIL) at home, offers a valuable look at how Canada is addressing the spread of terrorism to North America.

According to the NBC report, Canadian authorities are monitoring “hundreds” of people who have either gone to Syria to work with ISIS and similar groups and have returned, or have attempted to make the trip.

Although it begs the question: If Canada knows about terror suspects who have travelled out of the country, and as many as 80 more who have returned, why haven’t they done anything about it?

All of this comes at a high point in the threat of terrorist activity on North American soil.

Suspected members of ISIS have publicly urged supporters to attack Canada after the country attempted to deter residents from joining the terrorist group.

Canada, like the U.S., is also concerned about a recent propaganda video released by ISIS, which features an English-speaking suspect in the video the FBI believes is from either Canada or the U.S.

This issue of Canada’s “extremist travellers” was a key point in a government report titled, Public Report on the Terrorist Threat to Canada. The report notes that while the phenomenon has long existed, social networks and other media have made foreign conflicts more accessible to extremist travellers.

"Canada has not escaped this phenomenon, particularly given the ease of travel from Canada to conflict zones,” reads the report. “The need to address extremist travellers has become more pressing as these individuals participate in conflicts such as those in Syria, Somalia, Iraq and Afghanistan."

On the topic of those 80 people who left and returned to Canada and are suspected of terrorism-related activity, the report notes:

Some may have engaged in paramilitary activities. Others may have studied in extremist schools, raised money or otherwise supported terrorist groups. Some had their travel interrupted by financial issues, injuries or outside intervention and may plan to travel again. Some extremist travellers never achieved their goals and simply returned to Canada.

The growth of such travellers has, however, been behind several laws recently proposed and passed by the government. The Combating Terrorism Act enacted last year gives the government more ability to punish those who do participate in overseas violence. And a decision earlier this year to revoke the passports of those who participate in terrorist activity is focused on giving those people fewer places to hide.

“Given the barbaric nature of the groups operating now in Syria and Iraq, and their unscrupulous tactics, we need this kind of measure to prevent people from going down this misguided path, and to deter young people from even thinking about it,” Citizenship and Immigration Minister Chris Alexander said last month.

The struggle against these travellers is the purview of the RCMP-led High Risk Travel Case Management Group. The group follows a framework of how and when to take action against such suspects. They tailor their response to individual circumstances, with a focus on detecting and disrupting activity as early as possible.

When that is depends on many factors, from the readiness of the case against them, to the level of preparation put into their alleged plot, to the benefit of information security agencies receive by monitoring but not arresting such suspects.

But of more concern than the 80 suspects identified and monitored by the government are those who have neither been identified nor monitored by security groups. That is where the real danger lies.