For HLGuard support, look at the documentation of HLGuard. It is not an application that is supported here.
If you want to react to commands sent to the server (like amx_cvar), you can either write a plugin to catch them or you can modify the existing ones that implement the command you are looking to modify. However, most AMX Mod X commands can be restricted to specific users in your users.ini. rcon_password has a special exception in that it has extra requirement and cannot be modified with amx_cvar unless you also have RCON access in users.ini.
If you want a plugin created to react in certain ways, you can request that
here.
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