Praise be to Allah.
File downloading sites on the Internet may be used for good or bad, beneficial or harmful purposes. In cases such as this, one should refer to the principle of buying or renting things that may be used for halaal or haraam purposes:
It is permissible to sell subscriptions to those who it is known or thought most likely that they will use it for permissible purposes.
And it is haraam to sell them to those whom it is known or thought most likely that they will use it for haraam purposes, such as putting haraam images, indecent movies and so on.
If it is not known and the seller is uncertain and does not know whether the buyer will use it for halaal or haraam purposes, and there is nothing to indicate which of the two possibilities is more likely, then the basic principle is that the sale is valid and permissible, because Allaah says (interpretation of the meaning): “Allaah has permitted trading” [al-Baqarah 2:275].
Then if the buyer uses it for anything haraam, the sin of that is on him.
See the answer to question number 75007.
The owners of these websites should keep an eye on what is being placed on them and stipulate that no files which are forbidden according to sharee’ah are placed on them.
Our advice is that people should not work in this field, namely selling subscriptions, because even if he does not fall into haraam for certain, by selling them to people who will use them for evil and immoral purposes, he will be still uncertain as to whether his work is free from sin. The Prophet (blessings and peace of Allaah be upon him) said: “Leave that which makes you doubt for that which does not make you doubt.” Narrated by al-Tirmidhi (2518) and al-Nasaa’i (5711); classed as saheeh by al-Albaani in Saheeh al-Tirmidhi.
And he (blessings and peace of Allaah be upon him) said: “Whoever guards against the doubtful matters will protect his religious commitment from shortcomings and will protect his honour from slander, but whoever falls into that which is doubtful will fall into that which is haraam, like a shepherd who grazes his flock around prohibited land; he will soon graze in it.” Narrated by al-Bukhaari (52) and Muslim (1599).
And Allaah knows best.