The domain names like www-facebook-login.com and facebook-mails.com are designed to mislead and confuse the users who believe they're interacting with Facebook.
"By mentioning our apps and services in the domain names, OnlineNIC and ID Shield intended to make them appear legitimate and confuse people. This activity is known as cybersquatting and OnlineNIC has a history of this behaviour," Facebook said in a statement on Thursday.
The company has filed a lawsuit in California against the state-based OnlineNIC and its proxy service ID Shield.
"We don't want people to be deceived, so we track and take action against suspicious and misleading domains, including those registered using privacy/proxy services that allow owners to hide their identity," said Facebook.
There are tens of millions of domain names on the web that have been registered using these privacy/proxy services.
"We proactively report instances of abuse to domain name registrars and privacy/proxy services and often collaborate with them to take down these malicious domains," it added.
In many instances, however, domain name registrars and privacy/proxy services will not investigate or respond to abuse reports, which enables bad actors and delays our efforts to fight fraud and abuse.
"This was the case with OnlineNIC and ID Shield," said Facebook.
The lawsuit also references some 20 other domain names that are similar to Facebook and Instagram.
( With inputs from IANS )