InfiSTAR is the most commonly used admin tool and anti-hack for Arma 2 and 3.
The script is not free, but with the price it does include very frequent updates to ensure your server remains secure and your admin tools are up to date.
You can find it here: https://infistar.de/eng/index
The files also come with a readme file that has a full set of instruction to help you install infiSTAR step by step
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