private boolean hasLoggerFilter(final Configuration config) {
    for (LoggerConfig loggerConfig : config.getLoggers().values()) {
      boolean isRoot = loggerConfig.getName().isEmpty();
      boolean isGemFire = loggerConfig.getName().startsWith(GEODE_LOGGER_PREFIX);
      boolean hasFilter = loggerConfig.hasFilter();
      boolean isGemFireVerboseFilter =
          hasFilter && (GEODE_VERBOSE_FILTER.equals(loggerConfig.getFilter().toString())
              || GEMFIRE_VERBOSE_FILTER.equals(loggerConfig.getFilter().toString()));

      if (isRoot || isGemFire) {
        // check for Logger Filter
        if (hasFilter && !isGemFireVerboseFilter) {
          return true;
        }
      }
    }
    return false;
  }
Name of variable that is set to "true" in log4j2.xml to indicate that it is the default geode
config xml.
geode-log4j/src/main/java/org/apache/geode/logging/log4j/internal/impl/Log4jLoggingProvider.java