The patching technique used by keygens inherently mirrors the behavior of advanced persistent threats (APTs)—specifically process injection. Users are typically told to disable their antivirus to run these tools, which completely strips the host system of its defenses.
The "64bits exclusive" label indicates the tool was specifically compiled to run on and patch 64-bit versions of the software, which became the industry standard around 2012. Risk Profile: xf a2012 64bits exclusive