sub53 is a Lightening Fast multi-threaded subdomain hunter that uses CA certificates to Hunt Down subdomains
Now sub53 can also filter the alive subdomains from all the information gathered
$ sudo apt install git
$ git clone https://github.com/SxNade/sub53
$ cd sub53
$ chmod +x sub53
$ ./sub53 <domain1> <domain2>..................<domainN>
sub53 also saves the discovered subdomains to a text file for later use
Once Finished with finding subdomains, sub53 prompts the user for filtering the discovered subdomains
accordingly with the user action sub53 goes ahead and performs multithreaded filtering of the data.
This not only makes it Fast But also more reliable.
*sub53 depends on curl , install curl on your system
$ sudo apt install curl