<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 in a network? Context: A firewall is a security measure that blocks unauthorized access to a network while allowing authorized communication. Answer: [/INST]A firewall is designed to block unauthorized access while permitting authorized communications.</s>