Identifying the author of an anonymous post may require a Doe subpoena. This involves gaining access to the IP address of the poster via the hosting website. The courts can then order an ISP to identify the subscriber to whom it had assigned said IP address. Requests for such data are almost always fruitful, though providers will often effect a finite term of data retention (in accordance with the privacy policy of each—local law may specify a minimum and/or maximum term). The usage of IP addresses has, in recent times, been challenged as a legitimate way to identify anonymous users.