group" to pursue alleged pirate viewers. As some equipment (such as a computer interface to communicate with standard ISO/IEC 7816 smartcards) is useful for other purposes, this approach has drawn strong opposition from groups such as the Electronic Frontier Foundation. There have also been US counter-suits alleging that the legal tactics used by some DBS providers to demand large amounts of money from end-users may themselves appear unlawful or border on extortion. Much of the equipment is perfectly lawful to own; in these cases, only the misuse of the equipment to pirate signals is prohibited. This makes provider attempts at legal harassment of would-be pirates awkward at best, a serious problem for providers which is growing due to the Internet distribution of third-party software to reprogram some otherwise legitimate free-to-air DVB receivers to decrypt pay TV broadcasts with no extra hardware. US-based Internet sites containing information about the compromised encryption schemes have also been targeted by lawyers, often with the objective of costing the defendants enough in legal fees that they have to shut down or move their sites to offshore or foreign Internet hosts. In some cases, the serial numbers of unsubscribed smartcards have been blacklisted by providers, causing receivers to display error messages. A "hashing" approach of writing arbitrary data to every available location on the card and requiring that this data be present as part of the decryption algorithm has also been tried as a way of leaving less available free space for third-party code supplied by pirates. Another approach has been to load malicious code onto smartcards or receivers; these programs are intended to detect tampered cards and maliciously damage the cards or corrupt the contents of non-volatile memories within the receiver. This particular Trojan horse attack is often used as an ECM (electronic countermeasure) by providers, especially in North America where cards and receivers are sold by the providers themselves and are easy targets for insertion of backdoors in their computer firmware. The most famous ECM incident was the Black Sunday attack launched against tampered DirecTV "H" on 3 January 21, 2001 and intended to destroy the cards by overwriting a non-erasable part of the cards internal memory in order to lock the processor into an endless loop. The results of a provider resorting to the use of malicious code are usually temporary at best, as knowledge of how to repair most damage tends to