Working with Request Filter Logs
LiteSpeed filters requests using ModSecurity-type rules. (Does enable request filter use ModSecurity? The rulesets, I assume, are ModSecurity rulesets.) This page will guide you through setting up and adjusting logs for your request filters. These logs will help you test and debug your request filter (mod_security) rules. When the logs are properly set, you will be able to see what traffic is being rejected or passed by which rules.
For Native LSWS Configurations
Request filter logging is controlled in the WebAdmin console > (When you enable request filtering at a server level, what does that mean for a vhost level? Only enabled for LSWS native vhosts?)
For Apache Configurations
Request filtering for servers using Apache configurations is done through ModSecurity rules. Thus you will find debug information for those rules in your ModSecurity logs (and error logs). Usually, your ModSecurity logs are labeled XXXX. More information can be found in [https://github.com/SpiderLabs/ModSecurity/wiki/Reference-Manual|ModSecurity's documentation].