I imagine it's a hum removal program that filters the noise at its fundamental frequency as well as its overtones up the harmonic series (octave, fifth, second octave, etc.).
There are a lot of those programs. BIAS SoundSoap is a good one. Waves has a high-end one called x-Something that's also very good. Digidesign DINR. WaveLab and other editors have it built in, I believe. Logic PC was probably around long enough to have it. Arboretum Ionizer, plus they have a lower-end version. Many more.