: It may refer to a "combo list" or "leaked database" containing 600,000 credentials (emails/passwords) for specific websites or services.
RAR files are usually safe to use. But just like regular files, compressed files (RAR or ZIP) can also contain viruses or malware. How to Open RAR Files on Windows, Mac, and Mobile - Avast
: While the archive itself won't hurt your computer by just sitting there, extracting and running any .exe , .bat , or .scr files inside can trigger a virus.