How does Google keep tracts of their banned users

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Google bans people for violating their TOS. They keep tract of you when you get banned. You can never join again. How do they keep tract of you besides your name and address. Does anyone knows how they do it? I haven't tried appealing but I know that Google will reject it. They are so mean. I've experiences with them and I know that they're mean. Any experiences from you guys.