If you are currently working on this file, here is the standard process used in similar challenges:
Once opened, the archive usually contains images of cats. Analysts use several tools to find hidden data:
While "cats 3.rar" does not correspond to a single, universally famous challenge, it most likely refers to a multi-stage or forensics task where participants must find a "flag" (a specific string of text) hidden inside an archive. Likely Challenge Workflow
Searching the binary data of the file for readable text.