I'd suggest that you ask your ISP about this. I can find a Hitron (not Haltron) BRM 35202 & BRG3520... but neither of those is the model you've said you have. I can't find any info at all to tell me whether either of those devices has an internal firewall or supports UPnP... sorry.

Hopefully your ISP can tell you why your device is causing LW to show a firewall & help you to configure it