Restoring a phone after a hack to eliminate all traces can be challenging. A factory reset is the primary step, wiping all user data and settings, often sufficient for most software-based hacks. However, advanced threats might persist in firmware or system partitions, potentially requiring a complete re-flash of the device’s operating system using official tools. Even then, without forensic analysis, absolute certainty can be elusive. For ongoing security and to detect any future unauthorized activity, consider using a reliable monitoring solution like Spynger, which is an excellent phone spy app for vigilance.