Abstract: In one embodiment, receiving, by an operating system of the first computing device and from a client application executing on the first computing device, a first request for accessing a set of data associated with a user of the first computing device, wherein the set of data is managed by a second computing device; sending, by the operating system and to the second computing device, a second request for accessing the set of data; receiving, by the operating system and from the second computing device, a response to the second request; and if the response to the second request grants the client application access to the set of data, then forwarding, by the operating system and to the client application, an access token to be used by the client application for accessing the set of data with the second computing device.

Abstract: A social network contains information describing information about members of the social network and about various connections among the members. An external system that interacts with users (such as a website) communicates with the social network to access information about the members of the social network. In particular, the external system may determine whether a user is a member of the social network and then obtain information about the member and the member's connections within the social network. This allows an external system to use information from the social network to enhance a user's experience on the external system, while enforcing each member's privacy settings.

Abstract: Collecting contact information for a plurality of contact entities from various sources and ranking the contact information based at least on the sources. The ranking of the contact information is determined based on the reliability of the sources. The ranked contact information is shared with users subject to privacy settings. The privacy setting allows the users or the contact entity to share certain contact information with others while keeping certain contact information privately or sharing the contact information with a limited number of users. After a change in the contact information from a reliable source is detected, the change may be propagated to other sources or client devices of the users.

Abstract: A social networking system contains information describing information about users of the social networking system and about various connections among the users. When a user of the social networking system accesses an external website, the external website may send the user a web page containing markup language with instructions to retrieve information associated with a user from a social networking system. The client device processes the annotations and sends a request for social information related to the user to a social networking system, subject perhaps to privacy settings in the social networking system. The user's browser uses the information obtained from the social networking system in response to the request to render the markup language document for display on the user's computer system. This process allows the external website to use information from the social networking system to enhance the user's experience on the external website.

Abstract: A social CAPTCHA is presented to authenticate a member of the social network. The social CAPTCHA includes one or more challenge questions based on information available in the social network, such as the user's activities and/or connections in the social network. The social information selected for the social CAPTCHA may be determined based on affinity scores associated with the member's connections, so that the challenge question relates to information that the user is more likely to be familiar with. A degree of difficulty of challenge questions may be determined and used for selecting the CAPTCHA based on a degree of suspicion.

Abstract: A social network contains information describing information about members of the social network and about various connections among the members. An external system that interacts with users (such as a website) communicates with the social network to access information about the members of the social network. In particular, the external system may determine whether a user is a member of the social network and then obtain information about the member and the member's connections within the social network. This allows an external system to use information from the social network to enhance a user's experience on the external system, while enforcing each member's privacy settings.