Is it permissible for me not to remove the pornographic website blocking program that I installed, despite my father’s request to remove it, knowing that he is unaware that I discovered his addiction to these websites?

If the father accesses pornographic websites, his access to them must be blocked using software. It is not permissible to obey him if he asks for their removal because obedience is only due in matters of righteousness, and removing them would be aiding him in disobedience. They must remain in place as they are a means to prevent this evil, based on the Prophet's (peace be upon him) saying: "Whoever among you sees an evil, let him change it with his hand; if he is unable, then with his tongue; if he is unable, then with his heart—and that is the weakest of faith." Nevertheless, it is still obligatory to honor and be kind to the father and to supplicate for his guidance.