No security would be absolute, but a few simple (and cheap) precautions would greatly increase a party's survivability. I am advocating these goals: early detection of threats, ease of escape, and ease of setup, at the expense of actually damaging would-be attackers, since it sounds like the attackers are relatively strong and direct confrontation is to be avoided where possible.
Scheduled watches. Traveling in groups of three or more would allow them to set up scheduled watches of their camp, so that there is at least one pair of eyes scanning their surroundings to provide early warning of an attack to their sleeping comerades.
High (but not too high) ground. The advantage to high ground in this case is the visibility. Since the party is in a relatively sparse forest, they should choose locations that afford the best line of sight, that is, without dense clumps of trees or brush that could conceal an enemy advance. You don't want your location to be so high that you can't easily escape from it, though!
No fire at night. Cooking and boiling water is best done during the day, away from camp, as fires are very visible at night, and even then the smoke could well be detectable by your werewolves.
Concealment. You want to be downwind of those werewolves, for one thing.
Multiple escape routes. If you don't know with certainty where the enemy will approach from (rarely the case!), then you need multiple pre-planned escape routes. Choosing locations with the most naturally accessible escape routes will increase survivability.
There are a few defenses that might slow the enemy down:
Simple snare traps. Nothing elaborate, here, just a loop of rope here and there hidden in shallow snow. Even a length of twine tied taughtly between two trees would slow the enemy down when they trip on it, giving your party valuable seconds to get away. Combine these with noise-making objects like dry twigs, bones, whatever you can most easily scrounge.
Easily manually-deployable traps, making use of your surroundings. Kicking a log down a hill won't work every time, but if it's easy to set up and only takes half a second, it might be worth a try. If there's a natural pile of small rocks that can be tipped to make the enemy's approach more difficult, great! If there's a natural crevice or overhang you can conceal that might slow down the enemy, great! The point is, come up with creative terrain for your party to use to their advantage without spending precious calories and hours building. Having every encounter on flat ground with a few trees will lead to fairly predictable encounters.