<appender name="JSON_CONSOLE_APPENDER" class="ch.qos.logback.core.ConsoleAppender">
 <encoder class="a.b.c.logging.CustomLogbackEncoder">
  <providers>
   <timestamp/>
   <version/>
   <loggerName/>
   <threadName/>
   <logLevel/>
   <provider class="a.b.c.logging.LogMaskingProvider">
    <rules>
    <rule>
     <name>cc</name>
     <pattern>\d{13,18}</pattern>
    </rule>
    <rule>
     <name>SSN</name>
     <pattern>\s+\d{3}-?\d{3}-?\d{4}\s+</pattern>
    </rule>
    </rules>
   <userRules>
    <!-- Read custom user rules --->
    </userRules>
   </provider>
   <stackTrace/>
  </providers>
 </encoder>

public class Rules {

  private final Set<Rule> rules = new LinkedHashSet<>();

  public void addRule(Rule definition) {
    rules.add(definition.createRule());
  }

 ...
}

<userRules>   
<rule>
      <name>email</name>
      <pattern>([a-zA-Z0-9_\-\.]+)@[a-zA-Z0-9_\-\.]+\.[a-zA-Z]{2,5}</pattern>
   </rule>
   <rule>
    ...
</userRules>