<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:  Describe the purpose of firewall in computer security. Context: Firewalls act as a barrier between internal network and external threats. Answer: [/INST]It acts as a barrier between internal network and external threats.</s>