Following script enumaretes possible list of sub-domains using Securitytrails API
Register account in SecurityTrails.com
Activate Account to get the API Key
$ python subdomain-enum.py
Subdomain Enumeration Script
Enter Domain name : facebook.com
Please provide a file name to save : facebook.csv
$ head facebook.csv
unity.cta.grid.facebook.com
www-92.grid.facebook.com
wn05.grid.facebook.com
d.ns.c10r.facebook.com
transport.facebook.com
oldmutual.facebook.com
jilin.facebook.com
fna-internal-services-shv-02-fagc1.facebook.com
campus.facebook.com
presby.facebook.com
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Pull requests are welcome. For major changes, please open an issue first to discuss what you would like to change.