Most cameras found in "free" sharing groups are not "hacked" in the traditional sense; rather, they are discovered because of common security oversights:
Creating a Telegram group for IP camera (IPCam) integration is a highly efficient, free way to monitor security feeds or receive instant motion alerts directly on your phone. Telegram’s API allows it to act as a low-bandwidth monitoring hub simulated Dynamic DNS (DDNS) to track your camera's changing IP address. Core Uses for IPCam Telegram Groups Motion Alerts: ipcam telegram group free