SEKE 2012 Proceedings - Knowledge Systems Institute

users can control the reach of their tweets (videos) to a
particular individual; shown by a ‘̌’ against their private
scope. User groups scope, def ned by Facebook, Google+,
and Orkut, is similar but richer compared to the private
scope because it allows the selection of a specif c group
rather than an individual. Facebook, LinkedIn, and Orkut offer
additional scopes based on degrees of separation between
the owner of the data and its viewers. For example, Facebook
users can limit their photos to just friends, but make
wall posts visible to friends-of-friends as well. LinkedIn
users can share publicly, with only f rst-degree connections
or up to third-degree connections. Sharing with third-degree
connections may be equivalent to public sharing because
most OSN users are separated by less than four degrees [3].
Fb T G+ LI YT Ork
Up to 1st degree ̌ x x ̌ x ̌
Up to 2nd degree ̌ x x x x x
Up to 3rd degree x x x ̌ x x
Public ̌ ̌ ̌ ̌ ̌ ̌
Private x ̌ x x ̌ x
User Groups ̌ x ̌ x x ̌
3.3 User permissions
Table 4. Privacy scopes
Permissions authorize third parties to access information
that would otherwise be out of bounds because of users’ privacy
settings. All six OSNs use the OAuth protocol [8]
to manage these permissions. This protocol represents a
permission as an access token, which includes the specif
c information that is covered by the request, and a userdef
ned/OSN-specif ed expiration time. A dialogue displays
a summary of this information to the user. Upon receiving
user’s consent, the dialogue requests the OSN to create this
access token, which is then handed off to the requesting third
party. Each OSN def nes its permissions and customizes the
dialogue presentation and information summary. We study
these two attributes of user permissions across the APIs.
3.3.1 Permission types
We aggregate the permissions that third parties may request
into two types: data permissions and action permissions.
Data permissions grant access to users’ social data, while
action permissions allow third parties to perform tasks such
as uploading media, changing a prof le f eld, and posting
to social feeds on behalf of users. Each type of permission
has different implications; data permissions enable third parties
to harvest user information, whereas, action permissions
allow third parties to impersonate users. We identif ed 44
unique permissions; 29 data and 15 action. Table 5 shows
the number of permissions and their coverage for each OSN.
Number of permissions
Fb T G+ LI YT Ork
Data 28 7 15 0 0 1
Account 13 6 2 0 0 1
Coverage (%)
Data 95 80 80 - - 20
Account 85 100 65 - - 100
Table 5. Permission types – # and coverage
Facebook, Twitter, and Google+ exhibit high coverage
for both types of permissions. On Facebook, third parties
can request comprehensive permissions including authorizations
to access data when users are off ine, and to read the
stream of updates to social feeds of users’ connections. Although
Twitter’s purpose is public sharing, users can still
protect their tweets through explicit permissions. Retweets
and mention tags, however, can expose these tweets to third
parties with access to the tweets of users’ connections.
Orkut seeks a generic token which grants broad access to
all the prof le information, which does not have a friendsonly
privacy option. Third parties need to seek additional
permissions to extend this generic token to post to users’ social
feeds or to access their photos. LinkedIn and YouTube
users also cannot grant detailed data and action permissions,
but instead grant a generic token to access all information
that is not protected by a private scope. Thus, on LinkedIn
the generic access token provides third parties with the potential
to collect all personal information, and on YouTube it
allows third parties to upload videos, and even browse lists
of favorite and recommended videos. YouTube’s generic access
is worrisome because of its weak privacy control coverage
as seen in Table 3. LinkedIn, however, limits its generic
token by curtailing access to specif cprof le f elds through
comprehensive account-level privacy options.
3.3.2 Permission presentation
OSNs may seek broad data and action permissions from
their users to enable them to enter into favorable agreements
with third parties. Users, however, may be unwilling to grant
such broad permissions, and OSNs may try to circumvent
this reluctance through ambiguous permission dialogues.
Figure 2 displays a typical Facebook dialogue for an application
that desires access to a user’s prof le for registration
and login to an educational site for learning languages.
The application requests permission to retrieve all “basic”
Facebook data. The f gure also shows that this application
retrieved hometown, current city, religious views, work history,
and even relationship details from the user’s prof le.
Most of this basic information, however, is unnecessary for
registration/login or to teach languages. This collection is
additionally disturbing because many users probably do not
expect their consent to expose so many private details.
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