In some places, like Scandinavia, you can camp pretty much anywhere you like as long as it's only for one night and you don't leave a mess.
Is this also the case in Russia?
As far as I know (living in Latvia, used to be a part of USSR), it is not completely legal. The owners can call the police, but it usually doesn't go that far.
If you try to camp in a field or near a private lake, try to talk to somebody, if a home is in sight. If not, people in these parts are quite forthcoming and I've yet to get more than a grumpy "Just pick up after yourself."
A NOTE OF WARNING! Making fire pits is a whole another matter. Doing that on a private property without permission might very well land you in jail, or in other kind of trouble.
In short: Yes, but that doesn't stop decent people still doing it and living to tell the tale.