P2P-сети: Распространение данных и файлообмен

Data distribution using P2P networking technology

Peer to peer file sharing is the distribution and sharing of digital media using peer to peer (P2P) networking technology. P2P file sharing allows users to access media files such as books, music, movies, and games using a P2P software program that searches for other connected computers on a P2P network to locate the desired content. The nodes (peers) of such networks are end user computers and distribution servers (not required). The early days of file sharing were done predominantly by client server transfers from web pages, FTP and IRC before Napster popularised a Windows application that allowed users to both upload and download with a freemium style service. Record companies and artists called for its shutdown and FBI raids followed. Napster had been incredibly popular at its peak, spawning a grass roots movement following from the mixtape scene of the 80's and left a significant gap in music availability with its followers. After much discussion on forums and in chat rooms, it was decided that Napster had been vulnerable due to its reliance on centralised servers and their physical location and thus competing groups raced to build a decentralised peer to peer system. Peer to peer file sharing technology has evolved through several design stages from the early networks like Gnutella, which popularized the technology in several iterations that used various front ends such as Kazaa, Limewire and WinMX before Edonkey then on to later models like the BitTorrent protocol. Microsoft uses it for Update distribution (Windows 10) and online video games use it as their content distribution network for downloading large amounts of data without incurring the dramatic costs for bandwidth inherent when providing just a single source. Several factors contributed to the widespread adoption and facilitation of peer to peer file sharing. These included increasing Internet bandwidth, the widespread digitization of physical media, and the increasing capabilities of residential personal computers. Users are able to transfer one or more files from one computer to another across the Internet through various file transfer systems and other file sharing networks. Because this process occurred on a central server, however, Napster was held liable for copyright infringement and shut down in July 2001. It later reopened as a pay service. After Napster was shut down, peer to peer services were invented such as Gnutella and Kazaa. These services also allowed users to download files other than music, such as movies and games. Illegal darknets, including networks like Freenet, are sometimes considered to be third generation file sharing networks. Peer to peer file sharing is also efficient in terms of cost. The system administration overhead is smaller because the user is the provider and usually the provider is the administrator as well. Hence each network can be monitored by the users themselves. At the same time, large servers sometimes require more storage and this increases the cost since the storage has to be rented or bought exclusively for a server. However, usually peer to peer file sharing does not require a dedicated server.

The economic effect of copyright infringement through peer to peer file sharing on music revenue has been controversial and difficult to determine. Unofficial studies found that file sharing had a negative impact on record sales. It has proven difficult to untangle the cause and effect relationships among a number of different trends, including an increase in legal online purchases of music; illegal file sharing; drop in the prices of compact disks; and the closure of many independent music stores with a concomitant shift to sales by big box retailers.

The Motion Picture Association (MPAA) reported that American studios lost $2,373 billion in 2005 (equivalent to $ billion in ) representing approximately one third of the total cost of film piracy in the United States. The MPAA's estimate was doubted by commentators since it was based on the assumption that one download was equivalent to one lost sale, and downloaders might not purchase the movie if illegal downloading was not an option. Due to the private nature of the study, the figures could not be publicly checked for methodology or validity. In January 2008, as the MPAA was lobbying for a bill which would compel Universities to crack down on piracy, it was admitted by MPAA that its figures on piracy in colleges had been inflated by up to 300%. A 2010 study, commissioned by the International Chamber of Commerce and conducted by independent Paris based economics firm TERA, estimated that unlawful downloading of music, film and software cost Europe's creative industries several billion dollars in revenue each year. A further TERA study predicted losses due to piracy reaching as much as 1.2 million jobs and €240 billion in retail revenue by 2015 if the trend continued. Researchers applied a substitution rate of ten percent to the volume of copyright infringements per year. This rate corresponded to the number of units potentially traded if unlawful file sharing were eliminated and did not occur. Piracy rates for popular software and operating systems have been common, even in regions with strong intellectual property enforcement, such as the United States or the European Union.

In 2004, an estimated 70 million people participated in online file sharing. According to a CBS News poll, nearly 70 percent of 18 to 29 year olds thought file sharing was acceptable in some circumstances and 58 percent of all Americans who followed the file sharing issue considered it acceptable in at least some circumstances. In January 2006, 32 million Americans over the age of 12 had downloaded at least one feature length movie from the Internet, 80 percent of whom had done so exclusively over P2P. Of the population sampled, 60 percent felt that downloading copyrighted movies off the Internet did not constitute a very serious offense, however 78 percent believed taking a DVD from a store without paying for it constituted a very serious offense. In July 2008, 20 percent of Europeans used file sharing networks to obtain music, while 10 percent used paid for digital music services such as iTunes. In February 2009, a survey undertaken by Tiscali in the UK found that 75 percent of the English public polled were aware of what was legal and illegal in relation to file sharing, but there was a divide as to where they felt the legal burden should be placed: 49 percent of people believed P2P companies should be held responsible for illegal file sharing on their networks and 18 percent viewed individual file sharers as the culprits. According to an earlier poll, 75 percent of young voters in Sweden (18 20) supported file sharing when presented with the statement: "I think it is OK to download files from the Net, even if it is illegal." Of the respondents, 38 percent said they "adamantly agreed" while 39 percent said they "partly agreed". An academic study among American and European college students found that users of file sharing technologies were relatively anti copyright and that copyright enforcement created backlash, hardening pro file sharing beliefs among users of these technologies.

Communities have a prominent role in many peer to peer networks and applications, such as BitTorrent, Gnutella and DC++. There are different elements that contribute to the formation, development and the stability of these communities, which include interests, user attributes, cost reduction, user motivation and the dimension of the community.

Peer communities are formed on the basis of common interests. For Khambatti, Ryu and Dasgupta common interests can be labelled as attributes "which are used to determine the peer communities in which a particular peer can participate". There are two ways in which these attributes can be classified: explicit and implicit attributes. Explicit values are information that peers provide about themselves to a specific community, such as their interest in a subject or their taste in music. With implicit values, users do not directly express information about themselves, albeit, it is still possible to find information about that specific user by uncovering his or her past queries and research carried out in a P2P network. Khambatti, Ryu and Dasgupta divide these interests further into three classes: personal, claimed and group attributes. In their work Peer to peer File Sharing Communities, they explain that "the act of sharing is costly since any download from a sharer implies that the sharer is sacrificing bandwidth". Usefulness is a valued aspect by users when joining a P2P community. The specific P2P system must be perceived as "useful" by the user and must be able to fulfil his or her needs and pursue his or her interests. Consequently, the "size of the community of users defines the level of usefulness" and "the value of the system determines the number of users". One effort of the RIAA has been to implant decoy users to monitor the use of copyrighted material from a firsthand perspective.

In early June 2002, Researcher Nathaniel Good at HP Labs demonstrated that user interface design issues could contribute to users inadvertently sharing personal and confidential information over P2P networks. In 2003, Congressional hearings before the House Committee of Government Reform (Overexposed: The Threats to Privacy & Security on File Sharing Networks) and the Senate Judiciary Committee (The Dark Side of a Bright Idea: Could Personal and National Security Risks Compromise the Potential of P2P File Sharing Networks?) were convened to address and discuss the issue of inadvertent sharing on peer to peer networks and its consequences to consumer and national security. Researchers have examined potential security risks including the release of personal information, bundled spyware, and viruses downloaded from the network. Some proprietary file sharing clients have been known to bundle malware, though open source programs typically have not. Some open source file sharing packages have even provided integrated anti virus scanning. Since approximately 2004 the threat of identity theft had become more prevalent, and in July 2008 there was another inadvertent revealing of vast amounts of personal information through P2P sites. The "names, dates of birth, and Social Security numbers of about 2,000 of (an investment) firm's clients" were exposed, "including [those of] Supreme Court Justice Stephen Breyer." Furthermore, shortly before this security breach, the Today show had reported that more than 150,000 tax returns, 25,800 student loan applications and 626,000 credit reports had been inadvertently made available through file sharing. through legislation such as H. R. 1319, the Informed P2P User Act, in 2009. According to this act, it would be mandatory for individuals to be aware of the risks associated with peer to peer file sharing before purchasing software with informed consent of the user required prior to use of such programs. In addition, the act would allow users to block and remove P2P file sharing software from their computers at any time, with the Federal Trade Commission enforcing regulations. US CERT also warns of the potential risks. Nevertheless, in 2010, researchers discovered thousands of documents containing sensitive patient information on popular peer to peer (P2P) networks, including insurance details, personally identifying information, physician names and diagnosis codes on more than 28,000 individuals. Many of the documents contained sensitive patient communications, treatment data, medical diagnoses and psychiatric evaluations.

The act of file sharing is not illegal per se and peer to peer networks are also used for legitimate purposes. The legal issues in file sharing involve violating the laws of copyrighted material. Most discussions about the legality of file sharing are implied to be about solely copyright material. Many countries have fair use exceptions that permit limited use of copyrighted material without acquiring permission from the rights holders. Such documents include commentary, news reporting, research and scholarship. Copyright laws are territorial they do not extend beyond the territory of a specific state unless that state is a party to an international agreement. Most countries today are parties to at least one such agreement. In the area of privacy, recent court rulings seem to indicate that there can be no expectation of privacy in data exposed over peer to peer file sharing networks. In a 39 page ruling released November 8, 2013, US District Court Judge Christina Reiss denied the motion to suppress evidence gathered by authorities without a search warrant through an automated peer to peer search tool.

Media industries have made efforts to curtail the spread of copyrighted materials through P2P systems. Initially, the corporations were able to successfully sue the distribution platforms such as Napster and have them shut down. Additionally, they litigated users who prominently shared copyrighted materials en masse. However, as more decentralized systems such as FastTrack were developed, this proved to be unenforceable. There are also millions of users worldwide who use P2P systems illegally, which made it impractical to seek widespread legal action. One major effort involves distributing polluted files into the P2P network. For instance, one may distribute unrelated files that has the metadata of a copyrighted media. This way, users who downloads the media would receive something unrelated to what they have been expecting.