The command hashcat.exe -a 0 .\hash.txt .\rockyou.txt -r .\rules\replace.rule indicates that the penetration tester is using a dictionary attack combined with rule-based modifications. The -a 0 option specifies a dictionary attack mode, where .\rockyou.txt is the dictionary file containing potential passwords, and -r .\rules\replace.rule applies predefined rules to mutate these passwords. This method leverages a known list of potential passwords and augments them with additional variations based on the rules provided.
Reference:
Hashcat Dictionary Attack
Hashcat Rule-based Attack