Wazuh has a
repository for decoders, rules, rootchecks, etc. Almost all decoders/rules should work in every OSSEC version, except some of them that use new features. I recommend you to create a backup of OSSEC, then update the rules using the
script. Some rules will be failing, so replace them with the proper backup. In this way you will have the most up to date "signatures".
Regards.