misuses personal information extracted from OSNs to increase
the appearance of authenticity of traditional spam
messages. Brown et al. (2008) identified three context-aware
spam attacks: relationship-based attacks, unshared-attribute
attacks, and shared-attribute attacks. Relationship-based attacks
solely exploit relationship information, making this the
spam equivalent of social phishing. The two other attacks
exploit additional information from social networks, information
that is either shared or not shared between the spam
target and the spoofed friend. An example of an unshared
attack is birthday cards that seem to originate from the target's
friend. Shared attributes, e.g., photos in which both the
spam target and her spoofed friend are tagged, can be
exploited for context-aware spam. Huber et al. (2011a, 2011b)
found that the missing support for communication security
can be exploited to automatically extract personal information
from online social networks. Moreover, the authors
showed that the extracted information could be misused to
target a large number of users with context-aware spam.