How can I automatically extract NTLMv2 hashes from captured packets using Python?

Write a Python script using the `scapy` library to parse the pcap file. Filter packets with destination port 445 (SMB) and containing the string 'NTLMSSP'. From the NTLMv2 Response packet, extract the username, domain, HMAC-MD5, and blob at fixed offsets; the server challenge is obtained from the preceding packet. Assemble the hash in the format `username::domain:challenge:HMAC-MD5:blob` for cracking. The full implementation code is provided in Penetration Techniques - Using netsh to Capture NTLMv2 Hash from File Server Connections.