In general, companies like Apple challenge such requests, but in this case a grand jury and federal judge forced Apple to comply and keep it quiet.

Apple said it received a subpoena from a federal grand jury on Feb.

According to Apple, the subpoena did not provide details on the nature of the investigation.

"In this case, the subpoena, which was was issued by a federal grand jury and included a nondisclosure order signed by a federal magistrate judge, provided no information on the nature of the investigation and it would have been virtually impossible for Apple to understand the intent of the desired information without digging through users' accounts. Consistent with the request, Apple limited the information it provided to account subscriber information and did not provide any content such as emails or pictures.".

Apple also said that due to the nature of the subpoena, it believed other tech companies received similar orders from the DOJ.