The illicit use, copying, or distribution of copyrighted software is known as software piracy. It can take many different forms, including: End-user piracy refers to the unauthorized copying of legally acquired software products. Gaining unauthorized access to password-protected software, often known as "cracking," allows one to make multiple copies for their own use. Software cracking may be done by individuals, groups, companies or even government agencies. Software trafficking involves the sale of counterfeit software products over the Internet and through other channels (such as mail order). Software traffickers may produce poor quality copies of popular titles that look similar to those released by official distributors but are actually incomplete versions or pirate copies. They may also release complete versions of titles that have not been released in certain countries or regions. Finally, they may release titles with trademarks removed or replaced with generic terms (such as "movie" instead of "DVD version of Avatar"). Software leasing is the renting of computer software without ownership. This is most commonly seen in the educational market, where students pay a fixed monthly fee for the use of licensed software. They usually have limited time to use the software before it must be returned to the library. This saves money for schools because they do not have to purchase expensive software which does not get used. Software sharing is the lending of programs to friends or co-workers.