User:MorgothX/file sharing


 * See Shared resource for the conventional meaning of file sharing

File sharing refers to the providing and receiving of digital files over a network, usually following the peer-to-peer (P2P) model, where the files are stored on and served by personal computers of the users. Most people who engage in file sharing on the Internet both provide (upload) files and receive files (download).

P2P file sharing is distinct from file trading in that downloading files from a P2P network does not require uploading, although some networks either provide incentives for uploading such as credits or force the sharing of files being currently downloaded.

USENET
USENET was the first global file-sharing network. Files are posted to alt.binary.* groups by users and copies are propagated to all hosts that carry that particular group. Unlike the later peer-to-peer file sharing networks, requests for a file relies on people asking others to post them, and users save them if they want those files.

First P2P-generation: Server-client
The first generation of peer-to-peer file sharing networks had a centralized server system. This system controls traffic amongst the users. The servers store directories of the shared files of the users and are updated when a user logs on. In the centralized peer-to-peer model, a user would send a search to the centralized server of what they were looking for. The server then sends back a list of peers that have the data and facilitates the connection and download. The Server-Client system is quick and efficient because the central directory is constantly being updated and all users had to be registered to use the program. However, there is only a single point of entry, which could result in a collapse of the network. In addition, it is possible to have out of date information or broken links if the server is not refreshed.

The first file-sharing programs marked themselves by inquiries to a server, either the data to the download held ready or in appropriate different Peers and so-called Nodes further-obtained, so that one could download there. Two examples were Napster (today using a pay system) and eDonkey2000 in the server version (today, likewise with Overnet and KAD - network decentralized). Another notable instance of peer to peer file sharing, which still has a free version, is Limewire.

Web-based sharing
Webhosting is also used for file-sharing, since it makes it possible to exchange privately. In small communities popular files can be distributed very quickly and efficiently. Web hosters are independent of each other; therefore contents are not distributed further. Other terms for this are one-click hosting and web-based sharing.

File Sharing On The Social Graph
Recently, Facebook opened up its API to 3rd party developers that has allowed for a new type of file-sharing service to emerge. Box.net and FreeDrive.com are two examples of companies that have specific Facebook Applications that allow file sharing to be easily accomplished between friends.

Server-client-protocols

 * Audiogalaxy - Service ended in the middle of 2002.
 * Direct Connect
 * Napster - Closed in its original form in July 2001, since changed to a fee-based service.
 * Scour Exchange - The second exchange network after Napster. No longer exists.
 * Soulseek - Still popular today despite being relatively old, with more than 120,000 users online at any time.
 * TinyP2P - 15 lines Python - SOURCE code

Second P2P-Generation: Decentralization
After Napster encountered legal troubles, Justin Frankel of Nullsoft set out to create a network without a central index server, and Gnutella was the result. Unfortunately, the Gnutella model of all nodes being equal quickly died from bottlenecks as the network grew from incoming Napster refugees. FastTrack solved this problem by having some nodes be 'more equal than others'.

By electing some higher-capacity nodes to be indexing nodes, with lower capacity nodes branching off from them, FastTrack allowed for a network that could scale to a much larger size. Gnutella quickly adopted this model, and most current peer-to-peer networks implement this design, as it allows for large and efficient networks without central servers, Winmx also falls into this category.

Also included in the second generation are distributed hash tables (DHTs), which help solve the scalability problem by electing various nodes to index certain hashes (which are used to identify files), allowing for fast and efficient searching for any instances of a file on the network. This is not without drawbacks; perhaps most significantly, DHTs do not directly support keyword searching (as opposed to exact-match searching).

The best examples are Gnutella, Kazaa or eMule with Kademlia, whereby Kazaa has still a central server for logging in. eDonkey2000/Overnet, Gnutella, FastTrack and Ares Galaxy have summed up approx. 10.3 million users (as of April 2006, according to slyck.com). This number does not necessarily correspond to the actual number of persons who use these networks; it must be assumed that some use multiple clients for different networks.

Multi-Network-Clients


 * See Multi-network applications

Further networks or clients


 * See other networks

Third P2P-Generation: indirect and encrypted
The third generation of peer-to-peer networks are those that have anonymity features built in. Examples of anonymous networks are ANts P2P, RShare, Freenet, I2P, GNUnet and Entropy.

A degree of anonymity is realized by routing traffic through other users' clients, which have the function of network nodes. This makes it harder for someone to identify who is downloading or who is offering files. Most of these programs also have strong encryption to resist traffic sniffing.

Friend-to-friend networks only allow already-known users (also known as "friends") to connect to the user's computer, then each node can forward requests and files anonymously between its own "friends'" nodes.

Third-generation networks have not reached mass usage for file sharing because most current implementations incur too much overhead in their anonymity features, making them slow or hard to use. However, in countries where very fast fiber-to-the-home Internet access is commonplace, such as Japan, a number of anonymous file-sharing clients have already reached high popularity.

An example might be: Petra gives a file to Oliver, then Oliver gives the file to Anna. Petra and Anna thus never become acquainted and thus are protected. Often used virtual IP addresses obfuscate the user's network location because Petra only knows the virtual IP of Anna. Although real IP's are always necessary to establish a connection between Petra and Oliver, nobody knows if Anna really requested and Petra really send the file or if they just forward it (As long as they won't tell anyone their virtual IP's!). Additionally all transfers are encrypted, so that even the network administrators cannot see what was sent to whom. Example software includes WASTE, JetiANts, Tor and I2P. These clients differ greatly in their goals and implementation. WASTE is designed only for small groups and may therefore be considered Darknet; ANts and I2P are public Peer-to-Peer systems, with anonymization provided exclusively by routing reach.

Ants network
 * ANts P2P
 * JetiANts
 * Hornet

Mute network
 * MUTE
 * Kommute - KDE

I2P network
 * I2P
 * I2Phex - Gnutella over I2P
 * iMule - eDonkey (Kademlia) over I2P
 * Azureus - has I2P plugin

Retroshare-Network (F2F Instant Messenger)
 * Retroshare Instant Messenger - Retroshare Chat Messenger for privacy of filesharing'''

 other networks or clients 
 * Alliance
 * Freenet
 * GNUnet
 * Nodezilla
 * OFF System
 * Perfect Dark
 * Proxyshare
 * RShare
 * Share
 * Tor
 * WinNY
 * Zultrax

The fourth P2P-Generation: Streams over P2P
Apart from the traditional file sharing there are services that send streams instead of files over a P2P network. Thus one can hear radio and watch television without any server involved -- the streaming media is distributed over a P2P network. It is important that instead of a treelike network structure, a swarming technology known from BitTorrent is used. Best examples are Peercast, Miro, Cybersky and demo TV.

General
 * Broadcatching
 * Podcast

Tree structure
 * CoolStreaming
 * Peercast

Swarm structure such as BitTorrent
 * Djingle
 * Icecast
 * Joost
 * MediaBlog
 * PeerCast
 * PPLive
 * PPStream
 * SopCast
 * TVUPlayer
 * Vuze (client)

Copyright issues
File sharing has grown in popularity with the proliferation of high-speed Internet connections, and the relatively small file size and high-quality MP3 audio format. File sharing is a legal technology with legal uses, however many users use it to give and accept copyrighted materials without permission or authorization, and this is viewed by some as piracy of intellectual property, also known as copyright infringement.

Despite the existence of various international treaties, there are still sufficient variations between countries to cause significant difficulties in the protection of copyright. Recent years have seen copyright owners challenging file sharing networks, leading to litigation by industry bodies against private individual file sharers. The legal issues surrounding file sharing have been the subject of debate and conferences, especially among lawyers in the entertainment industries.

The challenges facing copyright holders in the face of file sharing systems highlight that current copyright law and enforcement may not be sufficient in dealing with rapidly developing new technologies and uses. Other challenges include ambiguities in the interpretation of copyright law and varying copyright legislations. The high number of individuals engaged in file sharing of copyrighted material means that copyright holders face problems relating to mass litigation and the development of processes for evidence and discovery.

File sharing technology has evolved in response to legal challenges. There are low technical barriers to entry for would-be sharers, and many file sharing approaches now obfuscate or hide the fact that sharing is happening, or the identities of those involved. For example: encryption and darknets. Furthermore it is contested whether the transfer of segmented files constitutes copyright infringement in itself based on existing laws. Further challenges have arisen because of the need to balance self-protection against fair use. A perceived overbalance towards protection (in the form of media that cannot be backed up, cannot be played on multiple systems by the owner, or contains rootkits or irksome security systems inserted by manufacturers), has led to a backlash against protection systems in some quarters. For example, the first crack of AACS was inspired by a perceived unfair restriction on owner usage.

Economic impact
As files sharing has spread a debate on how the infringement of copyright (in terms of file sharing copyrighted audio and visual content) impacts on legal distribution of especially music. In a broader context commentators have pointed out that the music industry, along with other types of media such as film and TV are having a difficult time adapting to the digital age.

Music Industry
A number of studies have found that file sharing has a negative impact on record sales. Examples of such studies include three papers published in the April 2006 issue of the Journal of Law and Economics (Liebowitz, Rob and Waldfogel, Zentner). Alejandro Zentner notes in another paper published in 2005 , that music sales have globally dropped from approximately $38 billion in 1999 to $32 billion in 2003, and that this downward trend coincides with the advent of Napster in June 1999. Using aggregate data Stan J. Liebowitz argues in a series of papers (2005, 2006) that file sharing had a significant negative impact on record sales.

However, a widely cited paper published in February 2007 concludes that file sharing has no negative effect on CD sales. This paper by Olberholzer-Gee and Strumpf, was published in the Journal of Political Economy, and is the only paper which analyzes actual downloads on file sharing networks. Data gathered from tracking downloading on OpenNap servers indicates that most users logged on very rarely and when they did log on they only downloaded a little more than one CD’s worth of songs. To show how these downloads affected album sales they tracked sales and downloads of 500 random albums of varying genres and after doing so found that illegal downloads would only be a small force in the decrease in album sales, possibly even slightly improving album sales of the top albums in stores at the time.

CNET News.com staff writer John Borland reports, “even high levels of file-swapping seemed to translate into an effect on album sales that was "statistically indistinguishable from zero". Some researchers believe that massive copying has been occurring ever since the invention of tape cassettes and the increased economic impact of simpler access to copying provided by computer networks does not seem to have been large..

In March 2007 the Wall Street Journal found that CD sales have dropped 20 percent in one year, which the Wall Street Journal interpreted as the latest sign of the shift in the way people acquire their music. BigChampagne LLC has reported that around one billion songs a month are being traded on illegal file-sharing networks. As a result of this decline in CD sales, a significant amount of record stores are going out of business and “...making it harder for consumers to find and purchase older titles in stores.”

The debate on how file sharing has impacted on the legal sale of music, especially CDs, is underlined by figures showing a decline in music or record stores. According to an article published by the Almighty Institute of Music Retail, an estimation of 900 independent record stores have closed since 2003, leaving 2,700 stores in the USA. Carolyn Draving, the owner of the record store Trac Records, which is closed after 32 years, believes the downfall is a direct result of the illegal internet downloads. She explains that she lost many long-time consumers to the internet and knows for certain that a few stopped coming in because they just downloaded instead. Another owner, Warren Greene of Spinsters Records, claims that nobody buys CD’s anymore and that most of his customers have turned to the internet in order to obtain their music.

Movie Industry
On May 31, 2006 the MPAA reported that American studios lost $2.3 billion to internet piracy in 2005, representing approximately one third of the total cost of film piracy in the United States. However, contrary to MPAA statements, several studies and commentators have concluded that one download hardly equals one lost sale, since many downloaders would not purchase the movie if illegal downloading were not an option. This is especially so as over 20 percent, $1.4 billion, of the $6.1 billion figure represents what is essentially making a non-commercial backups, either virtually on a device or physically on another disc, which is protected under United States law. These numbers are further suspicious due to the private nature of the study, which cannot be publicly checked for methodology or validity.

On January 22, 2008, it was revealed that the MPAA numbers on piracy in colleges was grossly inflated by up to 300%. This comes at a time when the MPAA are trying to push a bill through which would compel universities to crack down on piracy.

Software Industry
According to Moisés Naím, even in countries and regions with high intellectual property enforcement standards, such as the US or the EU, piracy rates of one-quarter or more for popular software and operating systems are common. The pirated software is distributed through file sharing at unprecedented rates, and according to Naím, software manufacturers dread the "one disc" effect: a phenomenon in which a single counterfeited copy can be propagated until it has taken over an entire country, pushing the legitimate product out of the market.

Public perception
According to a poll, 75% of young voters in Sweden (18-20) support 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% said they "adamantly agreed" while 39% said they "partly agreed".

In July 2008 the BBC reported that, according to Jupiter Research, a fifth of Europeans use file sharing networks. 10 percent use paid-for digital music services such as iTunes.

In the United States, the Solutions Research Group found that 32 million Americans over the age of 12 have downloaded at least one feature length movie from the Internet, 80 percent of whom have done so exclusively over P2P. Of the population sampled, roughly 40% believed that downloading copyrighted movies and music off the Internet constituted a "very serious offense."

In February 2008 The LA Times Blog published results of a US campus attitude survey which showed that 64 percent of respondents download music regularly through file-sharing networks and other unauthorized sources. The respondents were also asked to rate on a 1 to 7 scale "how nervous they were about being punished for illegal downloading" (1 being "not concerned" and 7 being "extremely concerned"), two-thirds answered 1 (43 percent) or 2 (24 percent). Only 4 percent answered 5 or 6, and none answered 7, "extremely concerned". This is even though RIAA (the Recording Industry Association of America) has sued thousands of students for file sharing since 2003.

Attacks on peer-to-peer networks
Many peer-to-peer networks are under constant attack by people with a variety of motives.

Examples include:
 * Poisoning attacks (e.g. providing files whose contents are different from the description, aka "spoofing")
 * Polluting attacks (e.g. inserting "bad" chunks/packets into an otherwise valid file on the network)
 * Defection attacks (users or software that make use of the network without contributing resources to it)
 * Insertion of viruses to carried data (e.g. downloaded or carried files may be infected with viruses or other malware)
 * Malware in the peer-to-peer network software itself (e.g. distributed software may contain spyware)
 * Denial of service attacks (attacks that may make the network run very slowly or break completely)
 * Filtering (network operators may attempt to prevent peer-to-peer network data from being carried)
 * Identity attacks (e.g. tracking down the users of the network and harassing or legally attacking them)
 * Spamming (e.g. sending unsolicited information across the network--not necessarily as a denial of service attack)
 * Distributed Denial of Service (a denial of service that attacks multiple host computers)
 * Man-in-Middle (the attacker intercepts files by obtaining the communication between two different users. Attackers can go on to change the information or simply pass it on untouched.  This is all done undetected)
 * Sybil attacks (the attacker creates one malicious identity that can be presented as multiple identities allowing the attacker to control a whole portion of the network)
 * Eclipse attack (the attacker first creates a large amount of users, allowing him to obtain control over a portion of the network. The attacker is then able to divide the network into different sub-networks. If the user wants to communicate with another user, it has to go through one of the attacker's many identities)

Most attacks can be defeated or controlled by careful design of the P2P network and through the use of encryption. P2P network defense is in fact closely related to the "Byzantine Generals Problem". However, almost any network will fail when the majority of the peers are trying to damage it, and many protocols may be rendered impotent by far fewer numbers.

Risks
Eric Johnson, Dan McGuire, and Nicholas D. Willey state some risks in their paper:
 * Your specific location does not play a role in Peer-to-Peer networks. It does not matter what country you are in files and threats have the ability to travel throughout the world.
 * Personal information is at risk because users expose certain files without knowledge that they are doing so. The main reasons these documents are at risk are due to “misplaced files, confusing interface design, Incentive to share a large number of files, general laziness on the part of the user, wizards designed to determine media folders, and poor organization habits”.
 * The growing network will soon make it impossible for users to be in control of security issues and thus the developers will not put an emphasis on it.
 * During traffic time on the Internet users tend to have multiple sites open at once, this runs the possibility of forgetting the sites that are up and leaves opportunity for the system to be compromised.
 * Second generation Peer-to-Peer file sharing networks now have the ability to search indexes using file names and information that is associated with the files. Thus, people can search files with search terms like “credit card” or other important information. This information can be taken easily and money could be stolen.

Some file-sharing software comes bundled with malware such as spyware, viruses, adware, or otherwise privacy-invasive software. Sometimes this unwanted software remains installed on the system even if the original file-sharing software is removed, and can be very difficult to eliminate. In many cases such malware can interfere with the correct operation of web browsers, anti-virus software, anti-spyware and software firewalls; can cause degraded performance on affected systems; and in some cases may secretly compromise a user's privacy or security. Malware is typically bundled with proprietary software, and not those in open source. In most cases it is possible to remove adware and spyware by running spyware removal programs. Such programs can often remove malware without influencing the functionality of the file-sharing software.

Some are also concerned about the use of file-sharing systems to distribute adult pornography to children, child pornography to anyone, inflammatory literature, and illegal or "unpopular" material. Novice users may find it difficult to obtain information about which networks, if any, are "safe" for them to use. With experience, users can reduce their exposure to offensive material by structuring their searches carefully (for example, a search limited to audio file types avoids exposure to video and image files).