Common passive ways to extract subdomains using a domain as input entrie.

prips() {
read -r a b c d e f g h <<< $(
ipcalc -nb "$1" | awk '/HostM/{print $2}' | tr '\n .' ' '
);
eval "echo {$a..$e}.{$b..$f}.{$c..$g}.{$d..$h}"
}

xargs -a hostslist -I@ sh -c 'ip=$(dig +short @); [ -z "${ip##10.}" ] && echo @'

xargs -P 500 -a hostslist -I@ sh -c 'dig @ | grep -q NOERROR 1>/dev/null && echo | echo @;'

xargs -P 500 -a hostslist -I@ sh -c 'nc -w1 -z -v @ 80 2>/dev/null && echo @'

xargs -P 500 -a hostslist -I@ sh -c 'nc -w1 -z -v @ 443 2>/dev/null && echo @' | xargs -I@ -P10 sh -c 'gospider -a -s "https://@" -d 2 | grep -Eo "(http|https)://[^/\\"]+" | anew'

xargs -P 500 -a hostslist -I@ sh -c 'nc -w1 -z -v @ 8443 2>/dev/null && echo @' | xargs -I@ -P10 sh -c 'gospider -a -s "https://@" -d 2 | grep -Eo "(http|https)://[^/\\"].*.js+" | sed "s#] - #\n#g" | anew'

xargs -P100 -a hostslist -I@ sh -c 'ip=$(dig +short @);[ ! -z "$ip" ] && printf "GET / HTTP/1.1\r\nHost: $ip\r\n\r\n" | timeout 2 openssl s_client -connect $ip:443 2>/dev/null' | sed 's# |/|=#\n#g' | grep paypal | anew

xargs -P 500 -a hostslist -I@ sh -c 'dig @' 2>/dev/null | awk -F'<<>>' '{print $3}' | xargs -n1 | tee -a hosts

cat hostUnicos.txt | while read line;do xargs -P 500 -a ../../subbrute/names_small.txt -I@ sh -c "dig +noidnout +noidnin +short @.$line | grep -c '^' 1>/dev/null && echo @.$line | tee -a hostsDig";done

xargs -P 100 -a hostUnicos -I@ sh -c 'sanssl @ 2>/dev/null | grep -v "No domains"'

Source: https://raw.githubusercontent.com/appsecco/the-art-of-subdomain-enumeration/master/san_subdomain_enum.py

dnsrecon -d alertmanager-1.staging.rtcdn.caffeine.tv -D /opt/SecLists/Discovery/DNS/subdomains-top1million-5000.txt -t brt~ (Doest seems to be so useful)

altdns -t 600 -w /opt/SecLists/Discovery/DNS/subdomains-top1million-5000.txt -i hostUnicos.txt -o hosts -r -s results_output.txt