  The question how to introduce thermal fluctuations in the equation of motion
of a magnetic system is addressed. Using the approach of the
fluctuation-dissipation theorem we calculate the properties of the noise for
both, the fluctuating field and fluctuating torque (force) representation. In
contrast to earlier calculations we consider the general case of a system of
interacting magnetic moments without the assumption of axial symmetry. We show
that the interactions do not result in any correlations of thermal fluctuations
in the field representation and that the same widely used formula can be used
in the most general case. We further prove that close to the equilibrium where
the fluctuation-dissipation theorem is valid, both, field and torque (force)
representations coincide, being different far away from it.
