The patch for RRDtool 1.0.28 is no longer available because 
Aberrant behavior detection is now a part of RRDtool 1.1.x, 
currently in development! Visit www.rrdtool.org for information
on RRDtool 1.1.x.

For those of already using the 1.0.28 patch, you can obtain the
latest version here: http://cricket.sourceforge.net/aberrant/rrd-1.0.28.aberrant.patch.gz