With the exception of early checkered historical relations (ie, the multiple US invasions of Canada in the Revolutionary War and War of 1812), Canada has always been an effective US ally and provided for a relatively secure northern border. However, given the nature of the threat of attacks through cyberspace, the cyber security of Canada is inextricably linked to that of the US.
The US and Canada share a number of common contact points within the critical infrastructure, including power grids, energy mediums and transportation. As the US seeks to increase cyber security, a portion of the discussion must center on Canada.
While it is highly unlikely (improbable) that the Canadian government would ever launch an attack against the US, cyber attackers could use Canada as another medium to access US based systems. In the case of a potential terrorist attack, often highlighted by Mike McConnell, former DNI, as an effort to shut down the US power grid, approaching through Canadian systems could be an easier target.
Since the power systems are linked between our two nations, an attack that shuts down the grid in Canada would likely have a cascading effect, cutting power to much of the North Eastern US.
Despite this threat, Canadians are taking the issues of cyber security as seriously as much of the rest of the world. The Canadians possess a cyber incident response center that handle a variety of tasks related to cyber threats.
The threat can also work in the other direction of course. A higher percentage of Canadians actually use the internet than their American counterparts and a cyber attack against US systems could cause problems in Canada.
One thing is for certain, there will need to be increased levels of cooperation between the US and Canada to effectively manage the threat to both countries from cyber attacks.