Now a days this happens generally that some outer world persons or nodes steals your domain name, but how can they make it possible then the answer is they could register YourDomainName.org, and do the same thing with Your Domain Name.biz, therefore contacting you and try to sell you those names at advanced prices. If that doesn't work, then the following events could happen.
They will allow your competitor to get a domain that sounds like yours, and allow him to cause confusion or try to steal your hard-earned traffic, business and clients. Take these steps right now to halt the cyber squatters.
Go through your domain name registrar and fill in a form that locks in authorized entities of your claim of other domain names. You can buy these names and keep them under your roof. In this way you can save your domain.