Typically, files with names like this claim to be "mods" or "hacks" for the browser-based game. Because Gartic.io is a web game, it doesn't usually require external .rar files to run. Most legitimate community scripts are shared via browser extensions like Tampermonkey, where you can actually read the code.
A compressed .rar file is a major red flag for several reasons: gartic.io_mod.rar
with a trusted antivirus like Malwarebytes or Windows Defender. Typically, files with names like this claim to