Should an employee who secretly misuses the internet be advised privately, or should their supervisor be informed, or should they be prevented from using the internet?

If it is proven that the employee accesses pornographic websites, he should be advised and warned privately. If he does not respond, there is no harm in informing the manager to take appropriate action, as scholars have permitted mentioning a person's fault to seek assistance in changing an evil (munkar) if it cannot be changed otherwise. Al-Nawawi said: "Backbiting is permissible for a legitimate purpose, such as seeking help to change an evil."