Use a tool like VirusTotal to check the file or the download link before interacting with it.
It is occasionally used as a shorthand for "Star Trek" (ST) or "Stick" (STK) related game assets or "mod-packs." ST3K.rar
If you have already opened it in a safe environment (like a Sandbox), look for a .txt file inside to explain the contents. Use a tool like VirusTotal to check the