tool to mask segments of low compositional complexity in amino acid sequences

 ncbi-seg (a.k.a. SEG) is a program for identifying and masking segments of
 low compositional complexity in amino acid sequences.
 .
 ncbi-seg divides sequences into contrasting segments of low-complexity and
 high-complexity. Low-complexity segments defined by the
 algorithm represent "simple sequences" or "compositionally-biased regions".
 .
 This program is inappropriate for masking nucleotide sequences and, in fact,
 may strip some nucleotide ambiguity codes from nt. sequences as they are being
 read.