"agrep" version 2.0.4 available via anonymous FTP
from sunsite.unc.edu (including source) has a
feature of cryptographic interest: fuzzy searches.
For example, agrep -2 cypherpunks newsgroupspooldirectory
would find all occurrence of"cypherpunks" or any such
pattern with up to two errors of substitution, addition
or deletion. cpyherpunks, cyphernks cipherapunks would
all be found, fer instance. And the thing is Boyer-Moore
sublinear FAST. Also has egrep features looking for up
to 30,000 (yes, thirty thousand) patterns simultaneously
with Boyer-Moore speed.
For the NSA the applications are obvious: look for a bounch
of keys words like revolution Timothy May NSA quickly.
For us a good initial use might be to screen out "bad" passwords
that are to simply a variant of a normal word. For example,
if agrep -3