Visit the following sites:
Password sniffing
Physical Access
DNS enumeration
host <domin>
nmap -T4 -p 53 --script dns-brute <domain>
dnsrecon -d <domain> -n 144.38.192.3
dnsrecon -r 144.38.192.3-144.38.192.200
Rainbow tables Salt vs no salt
openssl passwd -1 -salt pepper
or
openssl passwd -1
Might be fun to look at my git repo