<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 computer networks? Context: A firewall is a security measure used to protect networks from unauthorized access and attacks. Answer: [/INST]A firewall is used to protect a network from unauthorized access and attacks.</s>