As I mentioned in my recent post about the mmanon rewrite, I have been working on an offline anonymization tool. It is called SLFA (short for simple log file anonymizer) and I have now finished the first usable version.
SLFA is a java application that allows you to anonymize files from the command line. Currently, it can anonymize IPv4 addresses and IPv6 addresses (similar to the mmanon module of rsyslog) and can be configured to work with regular expressions.
It will be released shortly and would be glad about feedback once it has been released.