They are a common vector for hiding malware, trojans, or viruses.
The .part03.rar extension means this is the 3rd part of a larger, split RAR file.
What (game, movie, software) were you expecting it to be?
With more context, I can help you determine if it is safe to use or how to extract it.
Be extremely cautious when downloading split RAR files from unfamiliar sources:
Scan all parts with updated antivirus software before extracting them. To help you figure out what this file is, let me know: did you find or download this file? Do you have the other numbered parts that go with it?
To see what is inside, you must download all other parts (part01, part02, part04, etc.) in the set. ⚠️ Safety Warning
