  The Dendritic Cell Algorithm (DCA) is inspired by the function of the
dendritic cells of the human immune system. In nature, dendritic cells are the
intrusion detection agents of the human body, policing the tissue and organs
for potential invaders in the form of pathogens. In this research, and abstract
model of DC behaviour is developed and subsequently used to form an algorithm,
the DCA. The abstraction process was facilitated through close collaboration
with laboratory- based immunologists, who performed bespoke experiments, the
results of which are used as an integral part of this algorithm. The DCA is a
population based algorithm, with each agent in the system represented as an
'artificial DC'. Each DC has the ability to combine multiple data streams and
can add context to data suspected as anomalous. In this chapter the abstraction
process and details of the resultant algorithm are given. The algorithm is
applied to numerous intrusion detection problems in computer security including
the detection of port scans and botnets, where it has produced impressive
results with relatively low rates of false positives.
