Ensure your operating system and browser have the latest security patches.
Random strings of numbers followed by .rar or .zip are major red flags.
Warning: If You Receive "received_535813991618116.rar", Don’t Open It
Monitoring your keystrokes or accessing your webcam. Ransomware: Locking your files and demanding payment. What to do if you received it
If it came from a friend, their account has likely been hacked. Use a different communication method (like a text or phone call) to let them know.
As a precaution, update your passwords and enable Two-Factor Authentication (2FA) on all important accounts. How to stay safe in the future