Firewalls

• Prisons are a good theme for firewalls (singsing, shawshank, attica, etc)
• Mordac (Preventer of Information Services) from Dilbert
• Hagrid (Gatekeeper from Harry Potter)
• Norse_Mythology#Guards
• Cerberus (Greek mythology) the three-headed dog guarding the entrance to Hades; son of Typhon)