An adaptive finite-impulse-response filter includes a series of taps; each tap has a corresponding value of tap coefficient. Values of tap coefficients are calculated to minimize a system error function. The solution is under-constrained, and some values of tap coefficients can grow and cause overflow errors. Growth of tap coefficients is controlled by introducing tap leakage. Disclosed is a symmetric leakage algorithm, in which an updated value of the tap coefficient of a particular tap is based on the old value of the tap coefficient of the particular tap, on the old values of the tap coefficients of a set of taps preceding the particular tap, and on the old values of the tap coefficients of a series of taps following the particular tap.