There are several types of wolves with many subspecies as well. The gray wolf, also known as timber wolf, is a large wolf that can be found in parts of North America and Europe.
The eastern wolf is smaller than the gray wolf and can be found in Canada.
Wolves are adaptable and powerful creatures, and are capable of inflicting serious wounds even death when they attack.
Attacks on humans may occur, though not very often. Deaths have occurred in areas where human encroachment on their habitat has forced the wolves into changing their behaviors. Attacks don't normally end with someone being killed, but injured.
Unclean campsites may cause a wolf to become human habituated. Always keep a clean camp, for you and for the next person who will camp there. You'll also do the wolf a favor as well.
Just like in instances of bears becoming human habituated ending with undesirable encounters with humans, it can happen with wolves as well.
A truly wild wolf should pose very little risk to you as long as you respect its personal space and keep out of its way.
If a wolf approaches you, do not run but yell at it to attempt to scare it away. If it attacks fight back. It may go for your face and head so beware.
Obviously when wolves are in a pack they are naturally stronger.
Here are links to help you learn more about wolves.
1. Wild Sentry
2. Washington Nature Mapping Program - Gray Wolf