There is no such thing as a legitimate, permanently "free" McAfee product key. McAfee is a premium security service that requires a paid subscription for full features. However, you can legally access their protection for free through official trials and bundled offers. How to Legally Get McAfee for Free
The "long story" with free McAfee product keys is that they generally do not exist in a permanent, legal form outside of specific hardware bundles or limited-time trials. Most "free" keys found on public forums or lists are either one-time use keys already claimed, or part of a scam. How Free "Keys" Usually Work mcafee free product key