1. Introduction
The Internet has become the largest communication and in-
formation exchange medium. In our everyday life, communi-
cation has become distributed over a variety of online
communication channels. In addition to e-mail and IM
communication, Web 2.0 services such as Twitter, Facebook,
and other social networking sites have become a part of our
daily routine in private and business communication. Com-
panies expect their employees to be highly mobile and flexible
concerning their workspace (
Ballagas et al., 2004
) and there is
an increasing trend towards expecting employees and knowl-
edge workers to use their own devices for work, both in the
office and elsewhere. This increase in flexibility and,
conversely, reduction in face-to-face communication and
shared office space means that increasing amounts of data
need to be made available to co-workers through online
channels. The development of decentralized data access and
cloud services has brought about a paradigm shift in file
sharing as well as communication, which today is mostly
conducted over a third party, be it a social network or any other
type of platform. In this world of ubiquitous communication,
people freely publish information in online communication
and collaboration tools, such as cloud services and social
networks, with very little thought of security and privacy. They
share highly sensitive documents and information in cloud
services with other virtual users around the globe. Most of the
time, users consider their interaction partners as trusted, even
though the only identification is an e-mail address or a virtual
profile. In recent years, security vulnerabilities in online
communication and data sharing channels have often bee