( ) is a software application
that allows users
to make voice calls over
. Calls to other users of the service and, in some
countries, to free-of-charge numbers, are free, while calls to
and mobile phones
can be made for a fee. Additional
features include instant
, file transfer
written by Estonia-based
developers Ahti Heinla, Priit Kasesalu
and Jaan Tallinn, who had also
originally developed Kazaa.
Group, founded by Swedish-born
entrepreneur Niklas Zennström and the Dane Janus Friis, has its headquarters in Luxembourg, with offices in London, Tallinn, Tartu, Stockholm, Prague, and
One of the initial names for the project was "Sky peer-to-peer",
which was then abbreviated to "Skyper". However, some of the domain
names associated with "Skyper" were already taken. Dropping the
final "r" left the current title "Skype", for which domain names
Skype has experienced rapid growth in popular usage since the
launch of its services. The company was acquired by eBay
in September 2005 for $2.6 billion. eBay has
written Skype down to $1.7 billion on its books and announced a
public stock offering for 2010 to spin Skype off as a separate
company. Some media outlets have characterized the proposed sale
and ongoing provision of Skype as being under threat, because of a
software licensing dispute with the original creators. On September
1, 2009, a group of investors led by Silver Lake
bought 65% of Skype for
$1.9 billion. Later this amount was adjusted when eBay and the new
investors settled a lawsuit that had been brought by a holding
company set up by the original founders. It turned out that the
holding company had always owned the underlying peer-to-peer
technology. The lawsuit was eventually settled with ownership being
divided with the new investors owning 56%, the original founders
owning 14% and eBay retaining 30%.
Skype allows users to communicate by both voice, and more
traditional textual instant messaging. Voice chat allows both
calling a single user and conference calling. It uses a proprietary
codec. Skype's text chat client allows group chats, emoticons,
storing chat history, offline messaging and (in recent versions)
editing of previous messages. The usual gamut of features familiar
to instant messaging users - such as user profiles, online status
indicators, and so on - is also included.
SkypeIn allows Skype users to
receive calls on their computers dialed by regular phone
subscribers to a local Skype phone number; local numbers are
available for Australia, Brazil, Chile, Colombia, Denmark, the
Republic, Estonia, Finland, France, Germany, Hong Kong, Hungary, Ireland, Italy, Japan, Mexico, New Zealand, Poland, Romania, South Africa, South Korea, Sweden, Switzerland, the Netherlands, the United Kingdom, and the United States.
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. Some jurisdictions,
including France, Germany and South Africa, forbid the registration
of their telephone numbers to anyone without a physical presence or
residency in the country. .
users was introduced in January 2006 for the Windows
and Mac OS
platform clients. Skype 2.0 for Linux
released on March 13, 2008, also features support for video
Skype for Windows, starting with version 18.104.22.168, supports "High
Quality Video" with quality and features, e.g.
full-screen and screen-in-screen modes, similar to those of
mid-range videoconferencing systems. Skype audio conferences
currently support up to 25 people at a time, including the
A discontinued feature called "Skypecasting" allowed recordings of
Skype voice over IP
voice calls and
to be used as
, which allow audio or video
content to be syndicated over the Internet. Skype launched its
service in 2006. It remained in beta
until its end. Skypecasts hosted public conference calls, up to 100
people at a time. Unlike ordinary Skype p2p conference calls,
Skypecasts supported moderation features suitable for panel
discussions, lectures, and town hall forums. Skype operated a
directory of public Skypecasts. On August 26, 2008, Skype announced
that Skypecasts would be discontinued beginning September 1, 2008.
Skypecasts were shut down without any concrete explanation on 1
September 2008 at 12:00 UTC.
Skype does not provide the ability to call emergency numbers such
as 911 in the United States and Canada, 000 in Australia, 112 in
Europe, or 999 in the UK. The FCC
that, for the purposes of section 255 of the Telecommunications Act
is not an "interconnected VoIP provider". As a result, the U.S.
recommends that all VoIP users have an
analog line available as a backup.
Registered users of Skype are identified by a unique Skype
. Users may be listed in the Skype directory.
Skype clients applications and devices
- On April 24, 2008, Skype announced that they offer Skype on
around 50 mobile phones.
- On October 29, 2007, Skype launched its own mobile phone under
the brand name 3 Skypephone,
which runs a BREW OS.
- Skype is available for the N800 and
N810 Internet Tablets, which use the
- Skype is available on both the Sony
mylo COM-1 and COM-2 models.
- Skype is available for the PSP (PlayStation Portable) Slim and
Lite series, but the user needs to purchase a specially-designed
- The new PSP-3000 has a built in
microphone which allows communication without the Skype
- PSP Go has the ability to use Bluetooth connections with the Skype application,
in addition to its built-in microphone.
- Skype is available on mobile devices running Windows Mobile.
- The official Symbian version was under
development in 2006, but was not released.
- Official Skype support is available as part of X-Series together with mobile operator 3. However
this uses a regular mobile phone call and iskoot to a Skype
gateway, rather than mobile internet. Other companies produce
dedicated Skype phones which connect via WiFi.
- Third party developers, such as Nimbuzz
and Fring, have allowed Skype to run in
parallel with several other competing VoIP/IM networks (Nimbuzz has
even NimbuzzOut as competing paid service) in any Symbian or Java
environment. Nimbuzz has made Skype available to BlackBerry users.
- An official free Skype application for the iPhone OS was released in the iTunes store on
March 31 2009. However, some network operators do not allow Skype
calls to be made over their 3G network, restricting it to WiFi use
- September 2002, investment from Draper Investment Company and
at that time, original name was Skyper.
- April 2003, Skype.com and Skype.net domain names
- August 2003, First public beta version released.
- September 2005, SkypeOut banned in South China.
- October 2005, eBay purchased Skype (Oct
- December 2005, videotelephony
introduced. In April 2006, Number of registered users reaches 100
- October 2006, Skype 2.0 for Mac is released, the first full
release of Skype with video for Macintosh.
- December 2006: Skype announces a new pricing structure as of
January 18, 2007, with connection fees for all SkypeOut calls.
Skype 3.0 for Windows is released.
- In March 2007, Skype 3.1 is released, adding some new features,
including Skype Find and Skype Prime. Skype also released a 3.2
beta with a new feature called Send Money which allows users to
send money via PayPal from one Skype user to another.
- August 2007, Skype 3.5 for Windows released with additions such
as video in mood, inclusion of video content in chat, call transfer
to another person or a group, auto-redial.
- August 15, 2007, Skype 22.214.171.124 (beta) for Mac OS X released
adding availability of contacts in the Mac Address Book to the
Skype contact list, auto redial, contact groups, public chat
creation, and an in-window volume slider to the call window.
- August 16 / August 17, 2007, Skype users unable to connect to
full Skype network in many countries. Skype reports the system-wide
crash was the result of exceptional number of logins after a
Windows patch reboot ("Patch
- November 2007, Skype users are set to lose their 020 7 numbers after December 20, 2007.
- January 30, 2008, Skype released for the Sony PSP hand-held
- March 13, 2008, Skype 2.0 for Linux released with support for
- July 9, 2008, Skype 4.0 Beta is released, changing Skype into a
- September 1, 2008, Skype discontinues its SkypeCast service,
- September 8, 2008, The seventh season of the U.S. syndicated
game show Who Wants To Be
a Millionaire premieres, with a new Ask the Expert
lifeline that uses Skype for video chat.
- September 30, 2008, Skype 4.0 Beta 2 released, introducing
'Compact mode', after user criticism of the new default full-screen
- October 2, 2008: Analysis reveals TOM-skype sends content of
text messages and encryption keys to monitoring servers.
- November 2008, Skype added internal monthly and daily usage
caps on their SkypeOut subscriptions advertised as "Unlimited".
Many users and observers have commented on the high rate of dropped
calls, and the difficulty of reconnecting dropped calls. These are
most common for video calls and free (PC to PC) calls.
- Feb 6, 2009, Skype 4.0 is released.
- March 2009, Skype launched Skype for SIP, a service aimed at
business users. At the time of launch around 35% of Skype's users
were business users.
- April 14, 2009, eBay announced plans to spin off of Skype
through an initial public offering in 2010.
- August 1, 2009, Joltid files a motion with the US Securities
and Exchange Commission, seeking to terminate a licensing agreement
with eBay which allows eBay (and therefore Skype) to use the
peer to peer communications technology that Skype is based
on. If successful, this may cause a shutdown of Skype in its
- August 27, 2009, Skype releases an update to their more than
one year old Linux-client.
- September 1, 2009, eBay sells 65% of Skype to Index Ventures
and Silver Lake Partners.
- Early September 2009, Skype shuts down the Extras developer
Usage and traffic
||Total user accounts
|Active users — daily presence
|Skype to Skype minutes
Users may have more than one account, and it is not possible to
identify users with multiple accounts.
It was reported that 20,365,656 concurrent Skype users were online
as of November 9, 2009.
As of January 2009, Skype is available for Android
and over 100 Java enabled
mobile phones.As of January 2009, Skype is adding about 40 million
subscribers a quarter.
The volume of international traffic routed via Skype is
significant. It has become the largest international voice carrier.
Computer-to-computer traffic between Skype users in 2005 was 2.9%
of international carrier traffic in 2005 and about 4.4% of the
total international traffic of 264 billion minutes in 2006. In
2008, about 8% of cross-border calls were carried by Skype.
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
researchers have been able to watermark
the traffic so that it is
identifiable even after passing through an anonymizing network
SkypeNOW! is a service that Skype offers in South Africa to
customers with Vodafone
which can enable Vodafone users to engage in Skype international
voice calls wirelessly.
System and software
Skype uses a proprietary
Internet telephony (VoIP
) network, called the
. 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
corporation. The main difference
between Skype and standard VoIP clients is that Skype operates on a
model (originally based on
software), rather than the more
model. The Skype
user directory is entirely decentralized and distributed among the
of the network —
, users' computers — allowing the network to
scale very easily to large sizes (currently about 240 million
users) without a complex centralized infrastructure costly to the
Skype Group. The disadvantage of this approach is that Skype offers
no interoperability with SIP
-based VoIP networks.
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-Square Test and stochastic characterization
with Naïve Bayesian Classifiers are two approaches that were
published in 2007.
Skype uses an array of different audio compression methods
. Skype added a Skype-created codec called
to Skype for Windows 4 and other
Skype clients. SILK is intended to be "lightweight and
Skype is a secure
; encryption cannot be disabled, and is invisible
to the user. Skype reportedly uses non-proprietary, widely trusted
encryption techniques: RSA
for key negotiation
and the Advanced Encryption
to encrypt conversations. Skype provides an
uncontrolled registration system for users with absolutely no proof
of identity. This permits users to use the system without revealing
their identity to other users. It is trivial, of course, for
anybody 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 current security model.
Versions exist for Linux
, Linux-based Maemo
, Mac OS
(Intel and PPC), iPhone OS
and iPod Touch), Microsoft Windows
, Windows Mobile
), and even Sony's PSP
In an interview with Kurt Sauer, Chief Security Officer Skype, he
said, "We provide a safe communication option. I will not tell you
whether we listen or not." Skype's client uses an undocumented and
proprietary protocol. The Free
(FSF) is concerned by user privacy issues
arising from using proprietary software and protocols and has made
replacement for Skype one of their high priority projects. 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 program. Several media sources have reported that at a
meeting about the "Lawful interception of IP based services" held
on 25 June 2008, high-ranking but not named officials at the
Austrian interior ministry said that it was not a problem for them
to listen in on Skype conversations. Austrian broadcaster ORF,
citing minutes from the meeting, have reported that "the Austrian
police are able to listen in on Skype connections". Skype declined
to comment on the reports.
In the United States, the FCC
Assistance for Law Enforcement Act
as requiring digital phone
networks to allow wiretapping
presence of an FBI warrant, in the same way as traditional phone
service. Skype is not yet compliant with the act and has, so far,
stated that it does not plan to comply. According to the ACLU
, the Act is inconsistent with the original intent
of the Fourth
Amendment to the U.S. Constitution
recently, the ACLU has expressed the concern that the FCC
interpretation of the Act is incorrect.
On February 2009 Eurojust
on lawful interception
Service in People's Republic of China
September 2007, users in China trying to download the Skype software have been
redirected to the site of TOM, a joint
venture between a Chinese wireless operator and Skype, from which a
modified Chinese version can be downloaded.
The TOM client
participates in China's system of Internet
, monitoring text messages between Skype users in
China as well as messages exchanged with users outside the country.
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."
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
, Taiwan independence
and Chinese Communist Party
The saved messages contain personally identifiable
about the messages senders and recipients,
including IP addresses, usernames, land line phone numbers, and the
entire content of the text messages, including the time and date of
each message. This information was also saved for Skype users
outside China who were communicating with a TOM-Skype user. Because
of a server misconfiguration, these log files were for a time
accessible to the public.
There have been complaints about Skype's poor customer support. As
of September 2009, Skype does not provide any official means to
contact customer support, apart from indirect assistance through
its web portal only and contact email addresses. Skype is also
unable to update user billing information. Skype credit expires 180
days after the last charged call. Users are notified via email
before balances are removed, but some software issues have resulted
in some users not receiving notification. The Skype application
itself has no mechanism to indicate that the listed balance will
- Skype User Guide
- Skype: Skype Tests Software for Mass-Market Mobile
Phones, April 24, 2008
- Skype: 3 Skypephone Delivers Free Skype to Skype Mobile
Calls and Instant Messages at the Touch of a Button, October
- Skype: Skype Expands Mobile Strategy at 2008 International
CES, January 7, 2008
- Skype to Announce Disruptive Pricing Strategy for
SkypeOut Retrieved, December 19, 2006
- "Breaching Trust, An analysis of surveillance and
security practices on China’s TOM-Skype platform", Information
Warfare Monitor, October 2, 2008
- Skype is the limit thanks to recession,
accessed at 10 January 2009
- George Mason University
- " FSF High Priority Projects", Free
Software Foundation. Retrieved 2009-01-26.
- Biondi P., Desclaux F. " Silver Needle in the Skype", EADS Corporate
Research Center, 2006-03-02 to 2006-03-03. Retrieved
- Sokolov, David AJ. " Speculation over back door in Skype", Heise
Security UK, 2008-07-24. Retrieved 2009-01-26.
- Leyde, John" Austrian official fuels Skype backdoor
rumours", The Register UK, 2008-07-24 Retrieved
- Vilde, Boris" Skype Has Back Door for Cops' Eavesdropping",
Ohmproject, Sunday, 27 July 2008. Retrieved 2009-01-29.
- , TMCnet, September 24, 2007
- Surveillance of Skype messages found in China,
International Herald Tribune, October 2, 2008
- " Skype Defends VoIP IM Monitoring In China", by
Thomas Claburn, InformationWeek, October 2, 2008
- "Evidence Suggests China's SkypeIs Monitoring Internet
Messages", by Jason Dean, Wall Street Journal, October 2,
- Huge System for Web Surveillance Discovered in
China – NYTimes.com-By JOHN MARKOFF Published: October 1,