It does not seem to be appreciated that "a ferrite" is an extremely vague term.
The permeability of grades of ferrite varies ranges from about 10 to 20,000 depending on the design frequency. The size also varies from beads like the FX1115 to power transformer cores suitable for 100w or so.
Above the design frequency range the loss rises which is a rather hit or miss way to design a low-pass filter but , with luck, maybe useful for an unexpected problem.
