The database, with around 1.17 billion account details, was sold to Alex Holden, founder of security research firm Hold Security. Holden has previously uncovered data breaches for companies like JP Morgan and Adobe Systems.

Intriguingly, the hacker was ready to sell the database for USD 1, but gave it for free after getting a positive comment on his forum. 

This gives us an insight into how the hackers work worldwide. Hacking forums primarily work on Tor Onion router, aka 'dark web' as search engines like Google and Yahoo do not index them.

You can have access to such forums only if and after you have been endorsed by someone already who is a part of the group. The 'dark web' allows non-traceable discussions which can be both, a boon and a bane. The security officials and journalists benefit from such a platform because it allows work and interactions even on highly secured networks. 
However, it also becomes a breeding ground for potential hackers who use it to get away with any imminent probe. As far as this particular incident is concerned, the service providers themselves have not been hacked and the only people who need to worry are the ones who have used less secured websites in recent past from where their log-in ids and passwords became accessible to the hacker.