“Knock” is a python tool created to enumerate subdomains on a target system through a wordlist. It scans for DNS zone transfer and tries to bypass the wildcard DNS record automatically if it is enabled. Now Knock supports queries to VirusTotal subdomains. You can set the API_KEY within the “config.json” file.
To perform a necessary subdomain enumeration, use the following command: (root@kali:/opt/knock/knockpy# python3 knockpy.py exampledomain.com). It will list all possible subdomains for the website exampledomain.com and their running server names.
Always look for DNS subdomains that refer to services that aren’t in use in your configuration.