[fs0ci3ty]

Looking for any information on how to make a remote administration tool remain on the target's system and undetected.

Per say, a client is successfully installed on a machine (sys32 with admin rights), what extra steps can you take to make sure it doesn't get swept up by an AV installed later on
i.e. creating exclusions in windows defender/security.

Any insight would be greatly appreciated, thank you.

[k r o n o s]

You can use any crypter service. Your best bang is going to be a manual crypt by a reputable user.