WhatsApp and Telegram frequently use short alphanumeric codes for video files stored in your phone's "Sent" or "Received" folders.
Generic filenames are often used to disguise malware or phishing scripts. b358.mp4
If it was sent by a friend, ask them what the video contains before opening it. b358.mp4
(e.g., a tutorial, a meme, or news footage). What is the file size? b358.mp4
Apps like TikTok or Instagram often rename files upon download to unique strings of letters and numbers.