  Adversaries are abusing Internet security and privacy services to execute
cyber attacks. To cope with these threats, network operators utilize various
security tools and techniques to monitor the cyber space. An efficient way to
infer Internet threat activities is to collect information from trap-based
monitoring sensors. As such, this chapter primarily defines the cyberspace
trap-based monitoring systems and their taxonomies. Moreover, it presents the
state-of-the-art in terms of research contributions and techniques, tools and
technologies. Furthermore, it identifies gaps in terms of science and
technology. Additionally, it presents some case studies and practical
approaches corresponding to large-scale cyber monitoring systems such as
Nicter. We further present some related security policies and legal issues for
network monitoring. This chapter provides an overview on Internet monitoring
and offers a guideline for readers to help them understand the concepts of
observing, detecting and analyzing cyber attacks through computer network
traps.
