|Stable release||2.12.124 / June 11, 2015|
|Headquarters||Mountain View, California, United States|
WhatsApp is an instant messaging app for smartphones that operates under a subscription business model. The proprietary, cross-platform app uses the Internet to send text messages, images, video, user location and audio media messages.
WhatsApp Inc., was founded in 2009 by Brian Acton and Jan Koum, both former employees of Yahoo!. After Koum and Acton left Yahoo! in September 2007, the duo travelled to South America as a break from work. At one point they applied for a job at Facebook but were rejected. For the rest of the following years Koum relied on his $400,000 savings from Yahoo. In January 2009, after purchasing an iPhone and realizing that the seven-month-old App Store was about to spawn a whole new industry of apps, he started visiting his friend, Alex Fishman in West San Jose where the three would discuss "...having statuses next to individual names of the people," but this was not possible without an iPhone developer, so Fishman introduced Koum to Igor Solomennikov, a developer in Russia that he had found on RentACoder.com. Koum almost immediately chose the name "WhatsApp" because it sounded like "what’s up," and a week later on his birthday, on February 24, 2009, he incorporated WhatsApp Inc. in California. However, early WhatsApp kept crashing or getting stuck and at a particular point. Koum felt like giving up and looking for a new job, upon which Acton encouraged him to wait for a "few more months."
In June 2009, Apple launched push notifications, letting developers ping users when they were not using an app. Koum updated WhatsApp so that each time the user changed their statuses, it would ping everyone in the user's network. WhatsApp 2.0 was released with a messaging component and the active users suddenly swelled to 250,000. Koum visited Acton, who was still unemployed while managing another unsuccessful startup and decided to join the company. In October Acton persuaded five ex-Yahoo friends to invest $250,000 in seed funding, and as a result was granted co-founder status and a stake. He officially joined on November 1. After months at beta stage, the application eventually launched in November 2009 exclusively on the App Store for the iPhone. Koum then hired an old friend who lived in Los Angeles, Chris Peiffer, to make the BlackBerry version, which arrived two months later.
WhatsApp was switched from a free to paid service to avoid growing too fast, mainly because the primary cost was sending verification texts to users. In December 2009 WhatsApp for the iPhone was updated to send photos. By early 2011, WhatsApp was in the top 20 of all apps in Apple's U.S. App Store.
In April 2011, the founders agreed to take $7 million from Sequoia Capital on top of their $250,000 seed funding, after months of negotiation with Sequoia partner Jim Goetz. According to Goetz, the venture capital firm originally discovered WhatsApp through an App store tracking system they developed called 'early bird', at a time when the app was much more popular in other countries than in the US. However, it took months for the VC firm to track down Koum and Acton, given that the company didn't have a publicly available address nor signage at the time. All Goetz knew was that they were located in Mountain View, and Sequoia partners "literally walked the streets of Mountain View to see if [they] could intersect with [Koum and Acton]."
By February 2013, WhatsApp's user base had swelled to about 200 million active users and its staff to 50. Sequoia invested another $50 million, valuing WhatsApp at $1.5 billion.
In a December 2013 blog post, WhatsApp claimed that 400 million active users use the service each month. As of 22 April 2014, WhatsApp had over 500 million monthly active users, 700 million photos and 100 million videos are shared each day, and the messaging system handles more than 10 billion messages each day. On August 24, 2014, Koum announced on his Twitter account that WhatsApp had over 600 million active users worldwide. WhatsApp added about 25 million new users every month or 833,000 active users per day. With 65 million active users, about 10% of the total worldwide users, India is the largest single country in terms of number of users.
Acquisition by Facebook
On February 19, 2014, months after a venture capital financing round at a $1.5 billion valuation, Facebook announced it was acquiring WhatsApp for US$19 billion, its largest acquisition to date. Facebook, which was advised by Allen & Co, paid $4 billion in cash, $12 billion in Facebook shares, and an additional $3 billion in restricted stock units granted to WhatsApp's founders (advised by Morgan Stanley), Koum and Acton. Employee stock was scheduled to vest over four years subsequent to closing. The transaction was the largest purchase of a company backed by venture capitalists to date. Days after the announcement, WhatsApp users experienced a loss of service, leading to anger across social media.
The acquisition caused a considerable number of users to move, or try out other message services as well. Telegram claimed to have seen 8 million additional downloads of its app. Line claimed to have seen 2 million new users for its service.
At a keynote presentation at the Mobile World Congress in Barcelona in February 2014, Facebook CEO Mark Zuckerberg said that Facebook's acquisition of WhatsApp was closely related to the Internet.org vision. According to a TechCrunch article, Zuckerberg's vision for Internet.org was as follows: "The idea, he said, is to develop a group of basic internet services that would be free of charge to use – 'a 911 for the internet.' These could be a social networking service like Facebook, a messaging service, maybe search and other things like weather. Providing a bundle of these free of charge to users will work like a gateway drug of sorts – users who may be able to afford data services and phones these days just don’t see the point of why they would pay for those data services. This would give them some context for why they are important, and that will lead them to paying for more services like this – or so the hope goes."
On May 9, 2014, the government of Iran announced that it had proposed to block the access to WhatsApp service to Iranian residents. "The reason for this is the assumption of WhatsApp by the Facebook founder Mark Zuckerberg, who is an American Zionist," said Abdolsamad Khorramabadi, head of the country's Committee on Internet Crimes. Subsequently Iranian president Hassan Rouhani issued an order to the Ministry of ICT to stop filtering WhatsApp.
Just three days after announcing that WhatsApp had been purchased by Facebook, Koum said they were working to introduce voice calls in the coming months. He also advanced that new mobile phones would be sold in Germany with the WhatsApp brand, as their main goal was to be in all smartphones.
By early January 2015, WhatsApp reached a new milestone of 700 million monthly active users with over 30 billion messages being sent every day. In April 2015, Forbes predicted that between 2012-2018, the telecommunications industry will lose a combined total of $386 billion because of OTT services like WhatsApp and Skype. In the same month, WhatsApp had over 800 million active users.
After months at beta stage, the application eventually launched in November 2009 exclusively on the App Store for the iPhone. In January 2010, support for BlackBerry smartphones was added, and subsequently for Symbian OS in May 2010 and for Android OS in August 2010. In August 2011 a beta for Nokia Series 40 was added, making it the first non-smartphone OS with official WhatsApp support. A month later support for Windows Phone was added, followed by the BlackBerry 10 in March 2013. In April 2015, WhatsApp launched in the Tizen store, making it available for Samsung Tizen OS.
On January 21, 2015, WhatsApp launched a web client which can be used from the browser to send messages.
WhatsApp was made available on web browsers for the first time in late January 2015 through an announcement made by Koum on his Facebook page: "Our web client is simply an extension of your phone: the web browser mirrors conversations and messages from your mobile device—this means all of your messages still live on your phone". The WhatsApp user's handset must still be connected to the Internet for the browser application to function. As of January 21, 2015, the desktop version was only available to Android, Blackberry and Windows Phone users.
WhatsApp uses a customized version of the open standard Extensible Messaging and Presence Protocol (XMPP). Upon installation, it creates a user account using one's phone number as the username (Jabber ID:
WhatsApp software automatically compares all the phone numbers from the device's address book with its central database of WhatsApp users to automatically add contacts to the user's WhatsApp contact list. Previously the Android and S40 versions used an MD5-hashed, reversed-version of the phone's IMEI as password, while the iOS version used the phone's Wi-Fi MAC address instead of IMEI. A 2012 update now generates a random password on the server side.
WhatsApp is supported on most Android, BlackBerry, iPhone, and Nokia smartphones. All Android phones running the Android 2.1 and above, all BlackBerry devices running OS 4.7 and later, including BlackBerry 10, and all iPhones running iOS 4.3 and later. However, some Dual SIM devices may not be compatible with WhatsApp, though there are some workarounds for this.
In January 2015, WhatsApp introduced voice calling feature for Android, iOS and Windows app, it helped WhatsApp to attract a completely different segment. 
WhatsApp follows a ‘store and forward’ mechanism for exchanging messages between two users. When a user sends a message, it firstly travels to the server of WhatsApp where the message is stored. Then server repeatedly requests the receiver to acknowledge receipt of the message. As soon as message is acknowledged, server drops the message which means it is no longer available in database of server. WhatsApp server keeps the message only for 30 days in its database when it is not delivered to receiver (when receiver is not active on WhatsApp for 30 days).
Google Now is also going to support direct message sending protocol from its voice command. This service will be available on different messaging services and the highlighted one is Whatsapp. Google Now will provide this service for free and WhatsApp users will be able to send and receive messages on Google Now.
In May 2011, a security hole was reported which left WhatsApp user accounts open for session hijacking and packet analysis. WhatsApp communications were not encrypted, and data was sent and received in plaintext, meaning messages could easily be read if packet traces were available.
In September 2011, WhatsApp released a new version of the Messenger application for iPhones, closing critical security holes that allowed forged messages to be sent and messages from any WhatsApp user to be read.
On January 6, 2012, an unknown hacker published a website that made it possible to change the status of an arbitrary WhatsApp user, as long as the phone number was known. To make it work, it only required a restart of the app. According to the hacker, it is only one of the many security problems in WhatsApp. On January 9, WhatsApp reported that it had resolved the problem, although the only measure actually taken was to block the website's IP address. As a reaction, a Windows tool was made available for download providing the same functionality. This problem has since been resolved in the form of an IP address check on currently logged-in sessions.
On January 13, 2012, WhatsApp was removed from the iOS App Store, and the reason was not disclosed; however, the app was added back to the App Store four days later. WhatsApp was removed from Windows Phone store because of some technical problems, The app was added back to the Store on May 30, 2014.
In May 2012, security researchers noticed that new updates of WhatsApp no longer sent messages as plaintext, but the cryptographic method implemented was subsequently described as "broken". As of August 15, 2012, the WhatsApp support staff claim messages are encrypted in the "latest version" of the WhatsApp software for iOS and Android (but not BlackBerry, Windows Phone, and Symbian), without specifying the implemented cryptographic method.
German Tech site The H demonstrated how to use WhatsAPI to hijack any WhatsApp account on September 14, 2012. Shortly after, a legal threat to WhatsAPI's developers was alleged, characterized by The H as "an apparent reaction" to security reports, and WhatsAPI's source code was taken down for some days. The WhatsAPI team has since returned to active development.
On November 18, 2014, Open Whisper Systems announced a partnership with WhatsApp to provide end-to-end encryption by incorporating the encryption protocol used in their TextSecure application into each WhatsApp client platform. Open Whisper Systems asserted that they have already incorporated the protocol into the latest WhatsApp client for Android and that support for other clients, group/media messages, and key verification would be coming soon. WhatsApp confirmed the partnership to reporters, but there was no announcement or documentation about the encryption feature on the official website, and further requests for comment were declined.
On 1st December 2014, Indrajeet Bhuyan and Saurav Kar, both 17-year old teenagers, demonstrated the WhatsApp Message Handler Vulnerability, which allows anyone to remotely crash WhatsApp just by sending a specially crafted message of 2kb in size. To escape the problem, the user who receives the specially crafted message has to delete his/her whole conversation and start a fresh chat, because opening the message keeps on crashing WhatsApp unless the chat is deleted completely.
On January 21st 2015, WhatsApp launched a web client which can be used from the browser. It had two security issues that compromised user privacy: the WhatsApp Photo Privacy Bug and the WhatsApp Web Photo Sync Bug. 
On April 30, 2015, Heise Security published a report on WhatsApp's implementation of the TextSecure encryption protocol. They confirmed that the protocol has been implemented for Android-to-Android messages and that WhatsApp messages from or to iPhones are still not end-to-end encrypted. They expressed concern over the fact that regular WhatsApp users still can not tell the difference between end-to-end encrypted messages and regular messages.
As of June 12, 2015, WhatsApp scored 2 out of 7 points on the Electronic Frontier Foundation's secure messaging scorecard. It lost points because communications are not encrypted with a key the provider doesn't have access to, users can't verify contacts' identities, past messages are not secure if the encryption keys are stolen, the code is not open to independent review, and the security design is not properly documented.
A major privacy and security problem has been the subject of a joint Canadian-Dutch government investigation. The primary concern was that WhatsApp required users to upload their mobile phone's entire address book to WhatsApp servers so that WhatsApp could discover who, among the users' contacts, is available via WhatsApp. While this is a fast and convenient way to quickly find and connect the user with contacts who are also using WhatsApp, it means that their address book was then mirrored on the WhatsApp servers, including contact information for contacts who are not using WhatsApp. This information was stored in hashed, though not salted form and without "additional" identifying information such as a name, although the stored identifying information is sufficient to identify every contact.
On March 31, 2013 the Saudi Arabian Communications and Information Technology Commission (CITC) issued a statement regarding possible measures against WhatsApp, among other applications, unless the service providers took serious steps to comply with monitoring and privacy regulations.
A user does not need to send a friend request to send messages to another user.
In November 2014, WhatsApp introduced a new feature known as Read Receipts which alerts senders when their messages are read by recipients. Within a week, WhatsApp introduced an update allowing users to disable this feature.
In February 2014, the public authority for data privacy of the German state of Schleswig-Holstein has advised against using WhatsApp, as the service lacks privacy protection such as end-to-end client side encryption technology.
In February 2015, a Dutch university student named Maikel Zweerink published an app that set out to prove that anyone can track a WhatsApp user's status and also keep an eye of their changing profile pictures, privacy settings or status messages regardless of their privacy settings.
Criticism of business model
In response to the Facebook acquisition, Slate columnist Matthew Yglesias questioned whether the company's business model was viable in the United States in the long term. It had prospered by exploiting a "loophole" in mobile phone carriers' pricing. "Mobile phone operators aren't really selling consumers some voice service, some data service, and some SMS service", he explained. "They are selling access to the network. The different pricing schemes they come up with are just different ways of trying to maximize the value they extract from consumers." As part of that, they sold SMS separately. That made it easy for WhatsApp to find a way to replicate SMS using data, and then sell that to mobile customers for $1 a year. "But if WhatsApp gets big enough, then carrier strategy is going to change", he predicted. "You stop selling separate SMS plans and just have a take-it-or-leave-it overall package. And then suddenly WhatsApp isn't doing anything." However, the WhatsApp service would still provide value, if domestic texts were free, as users can still send free international texts, and WhatsApp also allows users to send their locations, audio/video files, and contacts.
In many markets outside the United States, WhatsApp is much more viable due to the existence of daily SMS fees or per-SMS fees, which make texting much more costly.
Competing with a number of Asian-based messaging services (like WeChat (468 million active users), Viber (209 million active users) and LINE (170 million active users)), WhatsApp handled ten billion messages per day in August 2012, growing from two billion in April 2012, and one billion the previous October. On June 13, 2013, WhatsApp announced that they had reached their new daily record by processing 27 billion messages. According to the Financial Times, WhatsApp "has done to SMS on mobile phones what Skype did to international calling on landlines."
In April 2014, WhatsApp crossed half-a-billion user mark.
As of May 2014, WhatsApp had crossed 50 million monthly active users in India, which is also its largest country by the number of monthly active users.
As of October 2014, WhatsApp has crossed 70 million monthly active users in India, which is 10% of its total user base (700 MM).
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