Islam strictly forbids any kind of violating the privacy of others whether though eavesdropping, spying, and listing to their talks against their will. The Qur’an made it clear that good believers must not involve in such acts. Thus, we find the verse: (O ye who believe! Shun much suspicion; for lo! some suspicion is a crime. And spy not, neither backbite one another. Would one of you love to eat the flesh of his dead brother? Ye abhor that (so abhor the other)! And keep your duty (to Allah). Lo! Allah is Relenting, Merciful.) (Al-Hujurat 49:12). The same warning could be found in the sunnah where we find a huge number of traditions discourage such acts.
There are many texts which condemn spying or listening to people’s talk against their will and seeking out people’s faults.
1 – It is narrated through Abu Hurayrah that the Prophet (peace and blessings be upon him) said: ‘Beware of suspicion, for suspicion is the falsest of speech. Do not eavesdrop; do not spy on one another; do not envy one another; do not forsake one another; do not hate one another. Be, O slaves of Allah, brothers.”
2 –The Prophet (peace and blessings upon him) said: “Whoever speaks of a dream that he did not actually see will be ordered [on the Day of Judgment] to tie two grains of barley together, and he will never be able to do so. Whoever listens in on other people’s conversations when they do not like that will have molten lead poured into his ears on the Day of Resurrection. Whoever makes an image will be punished and willbe ordered to breath life into it, and he will not be able to do so.”
A believer would read these traditions and then volunteer to spy on his fellow-Muslims, or seek out their faults, or spread mischief among them cannot be considered a good believer.
As for the application of the above-mentioned Hadith, it applies to all cases and Muslim is warned against deliberate listen to the talks of people while they are unaware or that was against their will. We should avoid such acts that would lead to unpleasant results in the Muslim community