The Application Gateway WAF team is announcing General Availability of Custom Rules for WAF_v2. Custom rules allow our customers to create their own rules with IP/IP range or String based matching conditions. For example, customers will be able to create rules which block requests from a specific IP range, or those matching a specific regular expression in the request’s header/cookie/URI/queryString/form elements. Users can also join multiple matching conditions into a single custom rule. In Vibranium, we will be augmenting Custom Rules to include Geo DB lists and IP reputation match conditions.
More details can be found here.