1. An apparatus comprising: a first circuit configured to (i) generate a first sample by filtering an input vector through a filter based on both (a) a filter vector and (b) an intermediate vector, each of a plurality of components in said intermediate vector having a respective random value, and (ii) generate a second sample as a difference between a third sample and said first sample, said third sample being received from a network as an echo; and a second circuit configured to update a subset of a plurality of taps of said filter based on a corresponding one of said components of said intermediate vector that has a particular value, wherein a number of elements of said subset is greater than a predetermined minimum number.