Discuss which third parties have access to centralized communication and how

[dbosk]

We write:

When using a centralized communications service, such as Facebook,
the level of security and privacy we can achieve is that the postman carries
non- transparent sacks. The business model of most such services is to read
peoples postcards to better profile their interests and thus deliver better suiting
advert- ising. Here, third parties cannot directly see who is communicating with
whom. They can only see that something goes to and from the service.
However, all information is available internally to the service. This means
that there are ways of learning this, for example through PRISM (Greenwald
and MacAskill
2013) of the US National Security Agency (NSA).

The reviewer comments:

%Which kind of third parties are these, when compared to the
%case of e-mail? Advertisers? Or other parties? And
%can advertisers read the content in e-mail systems? Google
%lets them advertise on keywords, but not read the mail
%itself for instance. Or hackers? 

This part has been rewritten so that this particular text is not longer there, but it's still interesting to explore further. Actually, Eve should be able to identify activists by using advertisements based on keywords.