This reads a line from STDIN, searches for IPv4 addresses, and replaces the last digit group with "0". It then appends the resulting line to the filename passed as first argument to this script.
This call:
111.222.333.444 foolog
... will append this line to the file foolog:
111.222.333.0
Make sure that anonymize-ip is in Apache's path or use an absolute path below:
ErrorLog "|anonymize-ip /opt/www/mysite/log/error.log"
CustomLog "|anonymize-ip /opt/www/mysite/log/access.log" combined