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Skype

Screenshot of Skype version 8 (14.32.55.0) for Windows desktop on Windows 10 in dark mode (contacts censored)
Original author(s)	Priit Kasesalu and Jaan Tallinn
Developer(s)	Skype Technologies
Initial release	29 August 2003; 15 years ago (2003-08-29)
Stable release(s) [±]
Windows, UWP 14.39.180.0 / 13 February 2019; 11 days ago (2019-02-13)[1] Windows, desktop 8.39.0.180 / 13 February 2019; 11 days ago (2019-02-13)[1] macOS 8.39.0.175 / 13 February 2019; 11 days ago (2019-02-13)[1] Linux 8.34.0.78 / 13 November 2018; 3 months ago (2018-11-13)[1] Android 8.39.0.185 / 13 February 2019; 11 days ago (2019-02-13)[2] iOS 8.39.0.175 / 13 February 2019; 11 days ago (2019-02-13)[2]
Operating system	Windows, macOS, Linux, Android, iOS, Windows Phone, HoloLens, Xbox One
Available in	108 languages[3]
Type	Videoconferencing, VoIP, and Instant messaging
License	Freemium
Alexa rank	416 (October 2018[update])[4]
Website	www.skype.com

Skype (/skaɪp/) is a telecommunications application software product that specializes in providing video chat and voice calls between computers, tablets, mobile devices, the Xbox One console, and smartwatches via the Internet and to regular telephones.^[5] Skype additionally provides instant messaging services. Users may transmit both text and video messages, and may exchange digital documents such as images, text, and video. Skype allows video conference calls.

Skype implements a freemium business model. Much of the service is free, but Skype Credit or a subscription is required to call a landline or a mobile phone number. At the end of 2010, there were over 660 million worldwide users, with over 300 million estimated active each month as of August 2015.^[6] At one point in February 2012, there were 34 million users concurrently online on Skype.^[7]

First released in August 2003, Skype was created by the Swede Niklas Zennström and the Dane Janus Friis, in cooperation with Ahti Heinla, Priit Kasesalu, and Jaan Tallinn, Estonians who developed the backend that was also used in the music-sharing application Kazaa. In September 2005, eBay acquired Skype for $2.6 billion.^[8] In September 2009,^[9]Silver Lake, Andreessen Horowitz, and the Canada Pension Plan Investment Board announced the acquisition of 65% of Skype for $1.9 billion from eBay, which attributed to the enterprise a market value of $2.92 billion. Microsoft bought Skype in May 2011 for $8.5 billion. Skype division headquarters are in Luxembourg, but most of the development team and 44% of all the division's employees are still situated in Tallinn and Tartu, Estonia.^[10][11][12]

Skype allows users to communicate over the Internet by voice, using a microphone, by video using a webcam, and by instant messaging. Skype-to-Skype calls to other users are free of charge, while calls to landline telephones and mobile phones (over traditional telephone networks) are charged via a debit-based user account system called Skype Credit. Some network administrators have banned Skype on corporate, government, home, and education networks,^[13] citing such reasons as inappropriate usage of resources, excessive bandwidth usage and security concerns.^[14]

Skype originally featured a hybrid peer-to-peer and client–server system.^[15] Skype has been powered entirely by Microsoft-operated supernodes since May 2012.^[16] The 2013 mass surveillance disclosures revealed that Microsoft had granted intelligence agencies unfettered access to supernodes and Skype communication content.^[17]

Throughout 2016 and 2017, Microsoft redesigned its Skype clients in a way that transitioned Skype from peer-to-peer service to a centralized Azure service and adjusted the user interfaces of apps to make text-based messaging more prominent than voice calling. Skype for Windows,^[18] iOS,^[19] Android,^[20] Mac^[21] and Linux^[22] received significant, visible overhauls.

Etymology

The name for the software is derived from "Sky peer-to-peer", which was then abbreviated to "Skyper". However, some of the domain names associated with "Skyper" were already taken.^[23] Dropping the final "r" left the current title "Skype", for which domain names were available.^[24]

History

Skype was founded in 2003 by Niklas Zennström, from Sweden, and Janus Friis, from Denmark.^[25] The Skype software was created by Estonians Ahti Heinla, Priit Kasesalu, and Jaan Tallinn. The first public beta version was released on 29 August 2003.^[26]

In June 2005, Skype entered into an agreement with the Polish web portal Onet.pl for an integrated offering on the Polish market.^[27] On 12 September 2005, eBay Inc. agreed to acquire Luxembourg-based Skype Technologies SA for approximately US$2.5 billion in up-front cash and eBay stock, plus potential performance-based consideration.^[28] On 1 September 2009, eBay announced it was selling 65% of Skype to Silver Lake, Andreessen Horowitz, and the Canada Pension Plan Investment Board for US$1.9 billion, valuing Skype at US$2.75 billion.^[29]

On 14 July 2011, Skype partnered with Comcast to bring its video chat service to Comcast subscribers via HDTV sets.^[30]

On 17 June 2013, Skype released a free video messaging service, which can be operated on Windows, Mac OS, iOS, Android and BlackBerry.^[31]

Microsoft acquisition

Skype icon, 2006-2012

Skype icon since 2012

On 10 May 2011, Microsoft Corporation acquired Skype Communications, S.à r.l for US$8.5 billion.^[32] The company was incorporated as a division of Microsoft, which acquired all its technologies with the purchase. The acquisition was completed on 13 October 2011.^[32][33]

Shortly after its acquisition, Microsoft began integrating the Skype service with its own products. Along with taking over development of existing Skype desktop and mobile apps, the company developed a dedicated client app for its newly released, touch-focused Windows 8 and Windows RT operating systems. They were made available from Windows Store when the new OS launched on 26 October 2012. The following year, it became the default messaging app for Windows 8.1, replacing the Windows 8 Messaging app at the time, and became pre-installed software on every device that came with or upgraded to 8.1. When the company introduced Office 2013 on 27 February 2013, it was announced that 60 Skype world minutes per month would be included in Office 365 consumer plans (Home and Personal, and University).

Furthermore, Microsoft discontinued two of its own products in favor of Skype: In a month-long transition period from 8 to 30 April 2013, Microsoft phased out its long-standing Windows Live Messenger instant messaging service in favor of Skype, although Messenger continued in mainland China.^[34][35] On 11 November 2014, Microsoft announced that in 2015, Lync would be replaced by Skype for Business. The latest version of the communication software combines features of Lync and the consumer Skype software. There are two user interfaces – organizations can switch their users from the default Skype for Business interface to the Lync interface.^[36]

Post acquisition

On 12 August 2013, Skype released the 4.10 update to the app for Apple iPhone and iPad that allows HD quality video for iPhone 5 and fourth-generation iPads.^[37]

On 20 November 2014, Microsoft Office's team announced that a new chat powered by Skype is going to be implemented in their software, giving tools to be able to chat with co-workers in the same document.^[38]

On 15 September 2015, Skype announced the release of Mojis, "a brand new way to express yourself on Skype". Mojis are short clips/gifs featuring characters from films and TV shows to be entered into conversations with the same ease as emoticons. They are working with Universal Studios, Disney Muppets, BBC and other studios to add to the available collection of Mojis.^[39]

On 21 December 2015, Gurdeep Singh Pall, Corporate Vice President of Skype, announced that Microsoft acquired the technology from Talko, "maker of an innovative mobile app for on-the-go business communications (...) Together, the new technology and talent will help us deliver great new features and capabilities in both Skype and Skype for Business."^[40]

In January 2016, Skype announced it would roll out free group video calling to users on mobile devices, including iOS and Android. In February 2016, Microsoft announced that it had started to introduce group calling on smartphones and tablets in North America and Western Europe.^[41]

In July 2016, Skype introduced an early Alpha version of a new Skype for Linux client, built with WebRTC technology, after several petitions had asked Microsoft to continue development for Linux.^[42][43]

On 30 September 2016, Skype updated their iOS app with new features, including an option to call contacts on Skype through Siri voice commands.^[44]

On 27 October 2016 Microsoft launched Skype for Business for Mac.^[45]

In February 2017, Microsoft announced plans to discontinue its Skype Wi-Fi service globally. The application was delisted, and the service itself became non-functional from 31 March 2017.^[46][47]

On 5 June 2017, Microsoft announced its plans to revamp Skype with similar features to Snapchat, allowing users to share temporary copies of their photos and video files.^[48]

In late June 2017, Microsoft rolled out their latest update for iOS, incorporating a revamped design and new third-party integrations, with platforms including Gfycat, YouTube, and UpWorthy.^[49] It was not well received, with numerous "1 star" reviews and complaints that the new client broke existing functionality.^[50]

In December 2017, Microsoft added "Skype Interviews", a shared code editing system for those wishing to run job interviews for programming roles.^[51][52]

Features

Registered users of Skype are identified by a unique Skype Name and may be listed in the Skype directory.^[53] Skype allows these registered users to communicate through both instant messaging and voice chat. Voice chat allows telephone calls between pairs of users and conference calling and uses a proprietary audio codec. Skype's text chat client allows group chats, emoticons, storing chat history, and editing of previous messages. Offline messages were implemented in a beta of version 5 but removed after a few weeks without notification. The usual features familiar to instant messaging users—user profiles, online status indicators, and so on—are also included.

The Online Number, a.k.a. SkypeIn, service allows Skype users to receive calls on their computers dialed by conventional phone subscribers to a local Skype phone number; local numbers are available for Australia, Belgium, Brazil, Chile, Colombia, Denmark, the Dominican Republic, Estonia, Finland, France, Germany, Hong Kong, Hungary, India, Ireland, Japan, Mexico, Nepal, New Zealand, Poland, Romania, South Africa, South Korea, Sweden, Switzerland, Turkey, the Netherlands, the United Kingdom, and the United States.^[54][55] A Skype user can have local numbers in any of these countries, with calls to the number charged at the same rate as calls to fixed lines in the country. The countries on this growing list are referred to collectively as the SkypeIn Countries.

Skype supports conference calls, video chats, and screen sharing between 25 people at a time for free.^[56][57]

Skype does not provide the ability to call emergency numbers, such as 112 in Europe, 911 in North America, or 100 in India and Nepal.^[58] However, as of December 2012, there is limited support for emergency calls in the United Kingdom, Australia, Denmark, and Finland.^[59] The U.S. Federal Communications Commission (FCC) has ruled that, for the purposes of section 255 of the Telecommunications Act, Skype is not an "interconnected VoIP provider".^[60] As a result, the U.S. National Emergency Number Association recommends that all VoIP users have an analog line available as a backup.^[61]

Usage and traffic

In January 2011, after the release of video calling on the Skype client for iPhone, Skype reached a record 27 million simultaneous online users.^[79] This record was broken with 29 million simultaneous online users on 21 February 2011^[80] and again on 28 March 2011 with 30 million online users.^[81] On 25 February 2012, Skype announced that it has over 32 million users for the first time ever.^[82] By 5 March 2012, it had 36 million simultaneous online users,^[83] and less than a year later, on 21 January 2013, Skype had more than 50 million concurrent users online.^[84]
In June 2012, Skype had surpassed 70 million downloads on an Android device.^[85]

On 19 July 2012, Microsoft announced that Skype users had logged 115 billion minutes of calls in the quarter, up 50% since the last quarter.^[86]

On 15 January 2014, TeleGeography estimated that Skype-to-Skype international traffic has gone up to 36% in 2013 to 214 billion minutes.^[87]

System and software

Client applications and devices

Windows app

Skype 4.0 (released 2009)

Multiple different versions of the Skype have been released for Windows since its conception. The original line of Skype applications continued from versions 1.0 through 4.0. It has offered a desktop-only app since 2003. Later, a mobile version was created for Windows Phones.

In 2012, Skype introduced a new version for Windows 8 similar to the Windows Phone version.^[88] On 7 July 2015 Skype modified the app to direct Windows users to download the desktop version of the app, but it was set to continue working on Windows RT until October 2016.^[89] In November 2015, Skype introduced three new apps, called Messaging, Skype Video, and Phone, intended to provide an integrated Skype experience in Windows 10.^[90][91] On 24 March 2016, Skype announced the integrated apps did not satisfy most users' needs and announced that they and the desktop app would eventually be replaced with a new UWP app,^[92] which was released as a preview version for the Windows 10 Anniversary Update and dubbed as the stable version with the release of the Windows 10 Creators Update.

The latest version of Skype for Windows is Skype 11, which is based on the Universal Windows Platform and runs on various Windows 10-related systems, including Xbox One, Windows phones, and Microsoft Hololens. Microsoft still offers the older Skype 8, which is Win32-based and runs on all systems from Windows XP (which is otherwise unsupported by Microsoft) to the most recent release of Windows 10.^[93]

In late 2017, this version was upgraded to Skype 12.9 in which several features were both removed and added.^[94]

Other desktop apps

• 
  macOS (10.9 or newer)^[93]


• 
  Linux (Ubuntu, Debian, openSUSE, Fedora)^[93]

Other mobile devices

• iOS


• Android


• 
  Nokia X^[95]

Skype was previously available on selected Symbian, BlackBerry OS and BlackBerry 10 devices. In May 2009 a Version 3.0 was available on Windows Mobile 5 to 6.1, and in September 2015 a Version 2.29^[96] was available on Windows Phone 8.1; in 2016 Microsoft announced that this would stop working in early 2017 once Skype's transition from peer-to-peer to client-server is complete.^[97]

Skype phones

On 29 October 2007, Skype launched its own mobile phone under the brand name 3 Skypephone, which runs a BREW OS.^[98]

Skype also offers a Skype Wi-Fi Phone, which is a wireless mobile phone that allows users to make Skype calls, using a wireless Internet connection. The Skype Wi-Fi Phone has an on-screen menu that lets Skype users see who is online and available to talk, similar to what is seen on a PC. It can also be used to talk with non-Skype users. SkypeOut minutes can be used to call any phone for a low price and no monthly fee. The Skype Wi-Fi phone does not contain a web browser and so can not access hotspots that require web-based login or authentication.^[99]

In December 2018 Skype announced it's going to add captions and subtitles during live calls. Features will appear in a real time. The company says a new feature will allow deaf people to use Skype audio and video calls.^[100]

Other platforms

• The Nokia N800, N810, and N900 Internet tablets, which run Maemo
  


• The Nokia N9, which runs MeeGo, comes with Skype voice calling and text messaging integrated; however, it lacks video-calling.


• Both the Sony mylo COM-1 and COM-2 models


• The PlayStation Portable Slim and Lite series, though the user needs to purchase a specially designed microphone peripheral. The PSP-3000 has a built-in microphone, which allows communication without the Skype peripheral.^[101] The PSP Go has the ability to use Bluetooth connections with the Skype application, in addition to its built-in microphone.^[102] Skype for PlayStation Vita may be downloaded via the PlayStation Network in the U.S. It includes the capability to receive incoming calls with the application running in the background.


• 
  Samsung Smart TV had a Skype app, which could be downloaded for free.^[103] It used the built-in camera and microphone for the newer models. Alternatively, a separate mountable Skype camera with built-in speakers and microphones is available to purchase for older models.^[104] This functionality has now been disabled along with any other "TV Based" Skype clients.


• Some devices are made to work with Skype by talking to a desktop Skype client or by embedding Skype software into the device. These are usually either tethered to a PC or have a built-in Wi-Fi client to allow calling from Wi-Fi hotspots, like the Netgear SPH101 Skype Wi-Fi Phone, the SMC WSKP100 Skype Wi-Fi Phone, the Belkin F1PP000GN-SK Wi-Fi Skype Phone, the Panasonic KX-WP1050 Wi-Fi Phone for Skype Executive Travel Set, the IPEVO So-20 Wi-Fi Phone for Skype and the Linksys CIT200 Wi-Fi Phone.

Third-party licensing

Third-party developers, such as Truphone, Nimbuzz, and Fring, previously allowed Skype to run in parallel with several other competing VoIP/IM networks (Truphone and Nimbuzz provide TruphoneOut and NimbuzzOut as a competing paid service) in any Symbian or Java environment. Nimbuzz made Skype available to BlackBerry users and Fring provided mobile video calling over Skype as well as support for the Android platform. Skype disabled Fring users from accessing Skype in July 2010.^[105] Nimbuzz discontinued support on request of Skype in October 2010.^[106]

Before and during the Microsoft acquisition, Skype withdrew licensing from several third parties producing software and hardware compatible with Skype. The Skype for Asterisk product from Digium was withdrawn as "no longer available for sale".^[107] The Senao SN358+ long-range (10–15 km) cordless phone was discontinued due to loss of licenses to participate in the Skype network as peers. In combination, these two products made it possible to create roaming cordless mesh networks with a robust handoff.

Technology

Protocol

Skype uses a proprietary Internet telephony (VoIP) network called the Skype protocol. The protocol has not been made publicly available by Skype, and official applications using the protocol are closed-source. Part of the Skype technology relies on the Global Index P2P protocol belonging to the Joltid Ltd. corporation. The main difference between Skype and standard VoIP clients is that Skype operates on a peer-to-peer model (originally based on the Kazaa software^[108]), rather than the more usual client–server model (note that the very popular Session Initiation Protocol (SIP) model of VoIP is also peer-to-peer, but implementation generally requires registration with a server, as does Skype).

On 20 June 2014, Microsoft announced the deprecation of the old Skype protocol. Within several months from this date, in order to continue using Skype services, Skype users will have to update to Skype applications released in 2014. The new Skype protocol—Microsoft Notification Protocol 24. The deprecation became effective in the second week of August 2014. Transferred files are now saved on central servers.

As far as networking stack support is concerned, Skype only supports the IPv4 protocol. It lacks support for the next-generation Internet protocol, IPv6.^[109]Skype for Business, however, includes support for IPv6 addresses, along with continued support of IPv4.^[110]

Protocol detection and control

Many networking and security companies claim to detect and control Skype's protocol for enterprise and carrier applications. While the specific detection methods used by these companies are often private, Pearson's chi-squared test and naive Bayes classification are two approaches that were published in 2008.^[111] Combining statistical measurements of payload properties (such as byte frequencies and initial byte sequences) as well as flow properties (like packet sizes and packet directions) has also shown to be an effective method for identifying Skype's TCP- and UDP-based protocols.^[112]

Audio codecs

Skype 2.x used G.729, Skype 3.2 introduced SVOPC, and Skype 4.0 added a Skype-created codec called SILK, intended to be "lightweight and embeddable".^[113] Additionally, Skype has released Opus as an open-source codec, which integrates the SILK codec principles for voice transmission with the CELT codec principles for higher-quality audio transmissions, such as live music performances. Opus was submitted to the Internet Engineering Task Force (IETF) in September 2010.^[114] Since then, it has been standardized as RFC 6716^[115]

Video codecs

VP7 is used for versions prior to Skype 5.5.^{[116][117][118][119][120]}

As of version 7.0, H.264 is used for both group and one-on-one video chat, at standard definition, 720p and 1080p high-definition.^[121][122]

Skype Qik

Skype acquired the video service Qik in 2011. After shutting down Qik in April 2014, Skype relaunched the service as Skype Qik on 14 October 2014. Although Qik offered video conferencing and Internet streaming, the new service focuses on mobile video messaging between individuals and groups.^[123]

Hyperlink Format

Skype uses URIs as skype:USER?call for a call.^[124]

Security and privacy

Skype was claimed initially to be a secure communication, with one of its early web pages stating "highly secure with end-to-end encryption".^[125] Security services were invisible to the user, and encryption cannot be disabled. Skype reportedly uses publicly documented, widely trusted encryption techniques: RSA for key negotiation and the Advanced Encryption Standard to encrypt conversations.^[126] However, it is impossible to verify that these algorithms are used correctly, completely, and at all times, as there is no public review possible without a protocol specification and/or the app source code. Skype provides an uncontrolled registration system for users with no proof of identity. Instead, a free choice of nicknames permits users to use the system without revealing their identities to other users. It is trivial to set up an account using any name; the displayed caller's name is no guarantee of authenticity. A third-party paper analyzing the security and methodology of Skype was presented at Black Hat Europe 2006. It analyzed Skype and found a number of security issues with the then-current security model.^[127]

PRISM: a clandestine surveillance program under which the NSA collects user data from companies like Skype and Facebook.^[128]

Skype incorporates some features which tend to hide its traffic, but it is not specifically designed to thwart traffic analysis and therefore does not provide anonymous communication. Some researchers have been able to watermark the traffic so that it is identifiable even after passing through an anonymizing network.^[129]

In an interview, Kurt Sauer, the Chief Security Officer of Skype, said, "We provide a safe communication option. I will not tell you whether we can listen or not."^[130] This does not deny the fact that the NSA monitors Skype conversations. Skype's client uses an undocumented and proprietary protocol. The Free Software Foundation (FSF) is concerned about user privacy issues arising from using proprietary software and protocols and has made a replacement for Skype one of their high-priority projects.^[131] Security researchers Biondi and Desclaux have speculated that Skype may have a back door, since Skype sends traffic even when it is turned off and because Skype has taken extreme measures to obfuscate their traffic and functioning of their app.^[132] Several media sources reported that at a meeting about the "Lawful interception of IP based services" held on 25 June 2008, high-ranking unnamed officials at the Austrian interior ministry said that they could listen in on Skype conversations without problems. Austrian public broadcasting service ORF, citing minutes from the meeting, reported that "the Austrian police are able to listen in on Skype connections". Skype declined to comment on the reports.^[133][134] One easily demonstrated method of monitoring is to set up two computers with the same Skype user ID and password. When a message is typed or a call is received on one computer, the second computer duplicates the audio and text. This requires knowledge of the user ID and password.

The United States Federal Communications Commission (FCC) has interpreted the Communications Assistance for Law Enforcement Act (CALEA) as requiring digital phone networks to allow wiretapping if authorized by an FBI warrant, in the same way as other phone services. In February 2009, Skype said that, not being a telephone company owning phone lines, it is exempt from CALEA and similar laws, which regulate US phone companies, and in fact, it is not clear whether Skype could support wiretapping even if it wanted to.^[135] According to the ACLU, the Act is inconsistent with the original intent of the Fourth Amendment to the U.S. Constitution;^[136] more recently, the ACLU has expressed the concern that the FCC interpretation of the Act is incorrect.^[137][138] It has been suggested that Microsoft made changes to Skype's infrastructure to ease various wiretapping requirements;^[139] however, Skype denies the claims.^[140]

Some time before Skype was sold in 2009, the company had started its own app, called Project Chess, to explore legal and technical ways to easily share calls with intelligence agencies and law enforcement.^[141]

On 20 February 2009, the European Union's Eurojust agency announced that the Italian Desk at Eurojust would "play a key role in the coordination and cooperation of the investigations on the use of internet telephony systems (VoIP), such as 'Skype'. ... The purpose of Eurojust's coordination role is to overcome the technical and judicial obstacles to the interception of internet telephony systems, taking into account the various data protection rules and civil rights"^[142]

In November 2010, a flaw was disclosed to Skype that showed how hackers could secretly track any user's IP address.^[143] Due to Skype's peer-to-peer nature, this was a difficult issue to address, but this bug was eventually remedied in a 2016 update.^[144]

In 2012, Skype introduced automatic updates to better protect users from security risks but received some challenge from users of the Mac product, as the updates cannot be disabled from version 5.6 on,^[145] both on Mac OS and Windows versions, although in the latter, and only from version 5.9 on, automatic updating can be turned off in certain cases.^[146]

According to a 2012 Washington Post article, Skype "has expanded its cooperation with law enforcement authorities to make online chats and other user information available to police"; the article additionally mentions Skype made changes to allow authorities access to addresses and credit card numbers.^[147]

In November 2012, Skype was reported to have handed over user data of a pro-WikiLeaks activist to Dallas, Texas-based private security company iSIGHT Partners without a warrant or court order. The alleged handover would be a breach of Skype's privacy policy. Skype responded with a statement that it launched an internal investigation to probe the breach of user data privacy.^[148]

13 November 2012, a Russian user published a flaw in Skype's security, which allowed any person to take over a Skype account knowing only the victim's email by following 7 steps.^[149][150] This vulnerability was claimed to exist for months and existed for more than 12 hours since published widely.

14 May 2013, it was documented that a URL sent via a Skype instant messaging session was usurped by the Skype service and subsequently used in a HTTP HEAD query originating from an IP address registered to Microsoft in Redmond (the IP address used was 65.52.100.214). The Microsoft query used the full URL supplied in the IM conversation and was generated by a previously undocumented security service.^[151] Security experts speculate the action was triggered by a technology similar to Microsoft's SmartScreen Filter used in its browsers.^[152]

The 2013 mass surveillance disclosures revealed that agencies such as the NSA and the FBI have the ability to eavesdrop on Skype, including the monitoring and storage of text and video calls and file transfers.^{[17][153][154]} The PRISM surveillance program, which requires FISA court authorization, reportedly has allowed the NSA unfettered access to its data center supernodes. According to the leaked documents, integration work began in November 2010, but it was not until February 2011 that the company was served with a directive to comply signed by the attorney general,^[17] with NSA documents showing that collection began on 31 March 2011.^[155]

On 10 November 2014, Skype scored 1 out of 7 points on the Electronic Frontier Foundation's secure messaging scorecard. Skype received a point for encryption during transit but lost points because communications are not encrypted with a key the provider doesn't have access to (i.e. the communications are not end-to-end encrypted), users can't verify contacts' identities, past messages are not secure if the encryption keys are stolen (i.e. the service does not provide forward secrecy), the code is not open to independent review (i.e. the code is not open-source), the security design is not properly documented, and there has not been a recent independent security audit.^{[156][157][158]}AIM, BlackBerry Messenger, Ebuddy XMS, Hushmail, Kik Messenger, Viber and Yahoo Messenger also scored 1 out of 7 points.^[156]

As of August, 2018, Skype now supports end-to-end encryption across all platforms.^[159]

Service in the People's Republic of China

Since September 2007, users in China trying to download the Skype software client have been redirected to the site of TOM Online, a joint venture between a Chinese wireless operator and Skype, from which a modified Chinese version can be downloaded.^[160] The TOM client participates in China's system of Internet censorship, monitoring text messages between Skype users in China as well as messages exchanged with users outside the country.^[161][162] Niklas Zennström, then chief executive of Skype, told reporters that TOM "had implemented a text filter, which is what everyone else in that market is doing. Those are the regulations." He also stated, "One thing that's certain is that those things are in no way jeopardising the privacy or the security of any of the users."^[163]

In October 2008, it was reported that TOM had been saving the full message contents of some Skype text conversations on its servers, apparently focusing on conversations containing political issues such as Tibet, Falun Gong, Taiwan independence, and the Chinese Communist Party. The saved messages contain personally identifiable information about the message senders and recipients, including IP addresses, usernames, landline phone numbers, and the entire content of the text messages, including the time and date of each message. Information about Skype users outside China who were communicating with a TOM-Skype user was also saved. A server misconfiguration made these log files accessible to the public for a time.^{[162][164][165]}

Research on the TOM-Skype venture has revealed information about blacklisted keyword checks, allowing censorship and surveillance of its users. The partnership has received much criticism for the latter. Microsoft remains unavailable for comment on the issue.^[166]

According to reports from the advocacy group Great Fire, Microsoft has modified censorship restrictions and ensured encryption of all user information.^[166] Furthermore, Microsoft is now partnered with Guangming Founder (GMF) in China.^[167]

All attempts to visit the official Skype web page from mainland China redirects to skype.gmw.cn. The Linux version of Skype is unavailable.

Localization

Skype comes bundled with the following locales and languages: Arabic, Bulgarian, Catalan, Chinese (Traditional and Simplified), Croatian, Czech, Danish, Dutch, English, Estonian, Finnish, French, German, Greek, Hebrew, Hungarian, Indonesian, Italian, Japanese, Korean, Latvian, Lithuanian, Nepali, Norwegian, Polish, Portuguese (Brazilian and European), Romanian, Russian, Serbian, Slovak, Slovenian, Spanish, Swedish, Thai, Turkish, Ukrainian, and Vietnamese.

As the Windows desktop app offers users the option of creating new language files, at least 80 other (full or partial) localizations are also available for many languages.^[168]

Customer service

As of February 2012, Skype provides support through their web support portal, support community, @skypesupport on Twitter, and Skype Facebook page. Direct contact via email and live chat is available through their web support portal. Chat Support is a premium feature available to Skype Premium and some other paid users.

In January 2010, Skype rescinded their policy of seizing funds in Skype accounts that have been inactive (no paid call) for 180 days. This was in settlement of a class-action lawsuit.^[169] Skype also paid up to US$4 to persons who opted into the action.

Skype's refund policy states that they will provide refunds in full if customers have used less than 1 euro of their Skype Credit. "Upon a duly submitted request, Skype will refund you on a pro rata basis for the unused period of a Product".

Skype has come under some criticism from users for the inability to completely close accounts. Users not wanting to continue using Skype can make their account inactive by deleting all personal information, except for the username.^[170]

Due to an outage happened on 21 September 2015, that affected several users in New Zealand, Australia and other countries, Skype decided to compensate their customers with 20 minutes of free calls to over 60 landline and 8 mobile phone numbers.^[171]

Educational use

Although Skype is a commercial product, its free version is used with increasing frequency among teachers and schools interested in global education projects.^[172] For example, Skype is being used to facilitate language exchange: students in different parts of the world are paired off, and each is a native speaker of the language that the other wishes to learn. In conversations over Skype, they alternate between the two languages.^{[173][174][175][176]}

Teachers are using Skype in unique ways to fulfil educational goals. The video conferencing aspect of the software is valuable in that it provides a way to connect students who speak different languages, hold virtual field trips, and reach out to experts in varying fields of study. These experiences allow students a chance to apply what they are learning in the classroom to real-life experiences, and it also achieves further learning opportunities.^[177][178]

Skype in the classroom is another free tool that Skype has set up on its website. It provides teachers with a way to make their classrooms more interactive and interesting. Skype in the classroom is a service that teachers can sign up for that will allow students to meet other students, talk to experts, and share ideas. Teachers can collaborate with other teachers around the world and design different learning experiences for their students. There are various Skype lessons, in which students can participate. Teachers can also use Skype's search tool and find experts in the field of their choice.^[179] Most of the schools in the United States and Europe often block Skype from the school network for students and hence students have left no option but to unblock it through various VPNs and proxy.

The nonprofit Paper Airplanes uses Skype to teach English to Syrian students. As of 2017, 320 pairs of students meet once a week using Skype as the platform for communication.^[180]

See also

• List of virtual communities with more than 100 million active users


• Caller ID spoofing


• Comparison of instant messaging clients


• Comparison of instant messaging protocols


• Comparison of VoIP software


• Mobile VoIP


• Presence information


• Unified communications


• List of video telecommunication services and product brands

References

External links

• 
  Official website