Microsoft’s servers maintain a master database. When you connect, your KV is checked against their list of "Live-enabled" consoles. If your KV is already flagged as "banned" or "never existed," you are rejected instantly.
: If you need a new KV.bin for an RGH/JTAG console, it must be purchased from a reputable seller who extracts them from physical, "scrapped" consoles. Legal and Terms of Service xbox 360 kv.bin generator