Usually, their repacks come with a pre-applied crack (often by SKIDROW, RELOADED, or CODEX), making the installation simple.
If you were a user searching for this term, here is a general troubleshooting methodology that was often prescribed: farcry4crackfixrepackrgmechanics link
Ensure your Windows Defender or third-party antivirus is active. Legacy cracks often trigger "False Positives" due to how they inject code into game files, but you must remain cautious. Usually, their repacks come with a pre-applied crack