What is the ruling of Islamic law on installing wiretapping (spy) devices on phones, what is the ruling on the perpetrator of such an act, and how does the law judge this crime?

The basic rule regarding espionage is that it is forbidden, based on the Almighty’s saying, “And do not spy,” and the Prophet’s (PBUH) saying, “Do not spy and do not eavesdrop.” However, it is permissible to spy on thieves, highway robbers, and those known for committing evil deeds, such as operating a liquor store or engaging in immoral acts. In such cases, the Muslim leader may send someone to spy on them. Therefore, planting surveillance devices in phones is not permissible except within these aforementioned limits. Whoever does so outside these limits is sinful.