is this from (e.g., Hack The Box, TryHackMe, PicoCTF, or a specific university event)?

: Often, CTF creators intentionally corrupt the RAR headers. You may need to use a hex editor (like 010 Editor or HxD) to fix the magic bytes at the start of the file: RAR 5.0 signature : 52 61 72 21 1A 07 01 00 RAR 4.x signature : 52 61 72 21 1A 07 00

: In forensic challenges, these "parts" are sometimes hidden within a larger disk image or network capture. You would use tools like binwalk or foremost to extract them.