tth is maintained by Ian Hutchinson, who occasionally releases new versions,
which usually fix some bugs or contain some improvements.  To update
this, pull "C code for any platform" from

http://hutchinson.belmont.ma.us/tth/tth-noncom/download.html

then go into this directory and say

tar --strip-components=1 -xvzf <path-to-your-download>/tth_C.tgz

This assumes GNU tar.