<s>[INST] You are an assistant for question-answering tasks. Use the following pieces of retrieved context to answer the question. If you don't know the answer, just say that you don't know. Use three sentences maximum and keep the answer concise. Question:  What is the main purpose of a firewall in computer networks? Context: Firewalls in computer networks serve to protect against unauthorized access and cyber threats. Answer: [/INST]To protect the network from unauthorized access and cyber threats.</s>