  The attack intensity of distributed denial of service (DDoS) attacks is
increasing every year. Botnets based on internet of things (IOT) devices are
now being used to conduct DDoS attacks. The estimation of direct and indirect
economic damages caused by these attacks is a complex problem. One of the
indirect damage of a DDoS attack can be on the market value of the victim firm.
In this article we analyze the impact of 45 different DDoS attack announcements
on victim's stock prices. We find that previous studies have a mixed conclusion
on the impact of DDoS attack announcements on the victim's stock price. Hence,
in this article we evaluate this impact using three different approaches and
compare the results. In the first approach, we use the assume the cumulative
abnormal returns to be normally distributed and test the hypothesis that a DDoS
attack announcement has no impact on the victim's stock price. In the latter
two methods, we do not assume a distribution and use the empirical distribution
of cumulative abnormal returns to test the hypothesis. We find that the
assumption of cumulative abnormal returns being normally distributed leads to
overestimation/underestimation of the impact. Finally, we analyze the impact of
DDoS attack announcement on victim's stock price in each of the 45 cases and
present our results.
