Your case seems extremely strange. Does the problem persist across reboots?
Mandiant is an actual company, and accordingly there is no information of any sort that they have just undertaken such an operation.
Meanwhile, several ransom ware families are using its name to hold user's PCs ransom. However, LG TVs run on a linux based OS, and I don't think there is any ransom ware disguising as Mandiant on the linux platform yet.
Off topic: Imagine a world where medical devices start becoming "smart" and ransom wares can literally hold your life ransom