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No, they are not legitimate. It is a SCAM and has been around for a few years. They will send you deceptive messages and trick you in to buying something from them and also they will access your computer and steal your files, documents, CC etc. They will say something like you have virus on your computer or your computer is at serious risk and they will ask you to install some application which would allow them to access your computer anytime they want.
No legitimate company does this. Don't take their call and ignore them. If you have any questions or would like any additional information, please don't hesitate to ask.
Remember, this is not my final answer. If my solutions didn't work please don't rate me bad or poor. Instead please reply back to me and I will continue to help you until we fix the problem or you are satisfied.