[editine]

I'm looking for a RAT which starts at startup and just runs an executable in the background with some parameters while watching a place on the internet for changes to the executable and/or the parameters to run it with. Windows is a must with macOS and Linux support nice. No need for spreading/remote file browsing/key logging/ddos/what have you.

[ExDeeMan]

Well, if you want something easy, some good free ones are njrat and revengerat. Just be sure not to infect anyone without permission!

[Baud]

I'm looking for a RAT which starts at startup and just runs an executable in the background with some parameters while watching a place on the internet for changes to the executable and/or the parameters to run it with. Windows is a must with macOS and Linux support nice. No need for spreading/remote file browsing/key logging/ddos/what have you.

You listed some of the features that almost every RAT has by default, except for the multi OS support, this is because most RATs are programmed in a .NET language (either C# or VB, I never saw a RAT written in Visual C++, but all these languages only work in Windows if the .NET framework is installed) since Linux and MacOS machines are way harder to infect with a software like a RAT and few people have interest in doing it anyway because the majority of users have a desktop PC with Windows installed, making it much easier to spread the RAT and have more slaves.

The autostart is an option you can select when building your server executable and without it it's pretty pointless to install a RAT in the first place, every RAT has this option, and the same goes for the ability of being in contact with the RAT client (or "master", it's the application you run to control the slaves) so that the program knows what task to perform and if needed it gives you some results or output back, for example, like you said, run an executable (that can be downloaded directly by the RAT if it's not present in your slave's computer) with certain parameters, and when you need to change said parameters you just edit the command with the parameters you need in that moment and resend the order to the slave, which will run the executable again with the wanted changes.

So basically every RAT on the market can do what you are looking for, you can download a free one and it's going to be very easy to accomplish what you want to do, unless you want to run it on MacOS computers, but I have never seen a RAT for it so far.

[editine]

I figured it was easier to just write my own for it, don't need anything too complex and this way it's guaranteed to not be fingerprinted yet.