<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 purpose of a firewall on a computer network? Context: Firewalls on a computer network serve to block unauthorized access and provide protection against cyber attacks. Answer: [/INST]To block unauthorized access and protect against cyber attacks.</s>