Args Analysis examines the characters found in arguments. Depending on its mode, it can block requests if unexpected characters are found, or pass them on to the WAF for further inspection. It can also act as an inverse content filter; those requests with arguments which contain only whitelisted characters can bypass WAF filtering.
Custom Signatures and Args Analysis will be deprecated in a future release. For content filtering, it is recommended that you use the first method based on Session Profiling instead.