Malware campaigns often use "DGA" (Domain Generation Algorithms) or simple randomization scripts to name their payloads. By using names like 55623.rar , 99281.rar , etc., attackers can:
Go to VirusTotal.com and upload the file. It will scan the archive against 70+ different antivirus engines. If more than 2 or 3 flag it, delete it immediately.
These are often sent via "phishing" emails disguised as invoices, shipping receipts, or "urgent" documents.