Line noise filters place an impedance mismatch between the line and the device, so that noise tends to reflect off it rather than pass through.
A good source of typical design info is in the datasheets for actual prepackaged filters. Simulating those designs in Spice will demonstrate what is going on inside those designs. If the data sheets do not have values, you may have to take a few filters apart and measure the component values. The inductors shown with a circular two ended arrow inside are transformers with two tightly coupled windings. These can have high inductance (no gaps in the core) for common mode noise currents (going the same way in each line) because the differential currents (the normal current that comes in one line goes through the load and goes back out the other line) produce canceling magnetic fields that do not magnetize the core. These, of course present little impedance in the way of normal load current harmonics.
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