“A foreign company (wand-du enterprises or whoever) is trying to purchase website domain names using your company and trademark names. However being the responsible and caring Domain Name Registration Service we are, we are first contacting you, the owner of the existing domains and trademarks, and will give you the amazing opportunity to get these website names first and therefore protect your brand. Oh, and by the way you only have 24hrs. to make up your mind”
It’s not really a scam as such, there is no mystery company and the domains they are “holding” for you are probably the dregs like yourdomain.biz or what have you. All it is, is yet another selling technique to prey on the naive and the less tech-savvy.
In all likelihood, if you really wanted the names you would have bought them in the first place and if you really do want them now (assuming they are indeed available) just go buy them from wherever you usually get them, it will probably be cheaper! You can’t “hold” a domain, it’s either registered or it isn’t.
Hope this helps.