Spam is becoming a more and more severe problem for individuals, networks,
organisations and businesses. The losses caused by spam are billions of dollars every
year. Research shows that spam contributes more than 80% of e-mails with an increased
in its growth rate every year. Spam is not limited to emails; it has started affecting other
technologies like VoIP, cellular and traditional telephony, and instant messaging services.
None of the approaches (including legislative, collaborative, social awareness and
technological) separately or in combination with other approaches, can prevent sufficient
of the spam to be deemed a solution to the spam problem.
The severity of the spam problem and the limitations of the state-of-the-Art solutions
create a strong need for an efficient anti-spam mechanism that can prevent significant
volumes of spam without showing any false positives. This can be achieved by an
efficient anti-spam mechanism such as the proposed anti-spam mechanism known as
"Spam Prevention using Access Codes", SPAC. SPAC targets spam from two angles i.e.
to prevent/block spam and to discourage spammers by making the infrastructure
environment very unpleasant for them.
In addition to the idea of Access Codes, SPAC combines the ideas behind some of the
key current technological anti-spam measures to increase effectiveness. The difference in
this work is that SPAC uses those ideas effectively and combines them in a unique way
which enables SPAC to acquire the good features of a number of technological anti-spam
approaches without showing any of the drawbacks of these approaches. Sybil attacks,
Dictionary attacks and address spoofing have no impact on the performance of SPAC. In
fact SPAC functions in a similar way (i.e. as for unknown persons) for these sorts of
An application known as the "SPAC application" has been developed to test the
performance of the SPAC mechanism. The results obtained from various tests on the
SPAC application show that SPAC has a clear edge over the existing anti-spam
A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.