Sellers often resell keys that have been leaked or purchased with stolen credit cards. Why "2050 Keys" are Risky
If you are interested in a specific feature, I can help you find: The for your region Instructions on how to activate a legitimate key
That said, here's a general overview and helpful information regarding Avast Premium Security and its licensing:
You can purchase 2-year or 3-year licenses directly from the Avast Store to save money while remaining fully supported.