report and the effectiveness of the incident response.
Second, it is difficult to make a correlation among
incidents and use the knowledge of these incidents.
At the stage of the lateral movement, several incidents
occur simultaneously at many sites. The general se-
curity manager collects reports from the sites, inves-
tigates the correlation among the incidents and makes
a decision on whether a critical cyber attack has oc-
curred or not. However, the lack of uniform quality
among reports, large distance, and time-zone differ-
ence among sites make the manager’s work difficult.
To solve these problems, we previously proposed
an incident response support system for multi-site net-
works(M. Kumazaki, H. Hasegawa, Y. Yamaguchi,
H. Shimada, and H. Takakura, 2021a). In this sys-
tem, both the security manager and the site admin-
istrator can obtain countermeasure recommendations
against the incident, an estimation of the correla-
tion of incidents across sites, and an identification
of the attacker’s objective, e.g., target device. To
enable recommendation of incident countermeasures,
we also proposed a method of evaluating the similar-
ity of incidents that occur at multiple sites(M. Ku-
mazaki, H. Hasegawa, Y. Yamaguchi, H. Shimada,
and H. Takakura, 2021b). In this previous study,
we compared similar cyber attacks regardless of their
progress and evaluated their similarity. The result
indicated the limitation of the conventional system.
When different stages of the incidents are observed at
the affected sites, this system did not correctly evalu-
ate the correlation of incidents among the sites.
We found that we could evaluate the similarity
among incidents with more precision if we divide the
information about a series of attacks into each attack
stage and compare the part of the same stages of the
incidents. In this paper, we propose an attack method
expectation method for estimating the attack meth-
ods and their execution times on the basis of the logs
caused by a cyber attack. This method uses a table
that summarizes attack methods, the logs caused by
those methods, and the importance of those logs. It
also compares this table with logs caused by a cy-
ber attack and calculates the probability of each attack
method.
We also propose a cyber attack stage tracing sys-
tem to extract logs caused by a cyber attack and di-
vide these logs into attack stages using the proposed
method. The system collects logs for a certain period
and extracts those caused by the cyber attack. The
system expects used attack methods from the logs by
the proposed method, and identifies the attack stage
of the attack. We examined the effectiveness of the
proposed method by conducting experiments using a
simulated cyber attack.
2 RELATED WORK
Our conventional system uses communication behav-
ior and various logs as evaluation indicators of inci-
dent similarity. These have also been used for detec-
tion methods of cyber attacks, and many studies have
been conducted on them. As for attack detection us-
ing communication behavior, a method for detecting
attacks using HTTP requests has been proposed(Y.
Kanemoto, K. Aoki, M. Iwamura, J. Miyoshi, D.
Kotani, H. Takakura, and Y. Okabe, 2019). This
method extracts the attack code from the HTTP re-
quest, and executes it in the sandbox. Finally, it com-
pares the execution result and actual HTTP response
to determine the success or failure of the attack. As
a system to detect cyber attacks using various logs,
there is Security Information and Event Management
(SIEM). This system not only centralizes the manage-
ment of various logs, but also enables early detection
of incidents by correlating and analyzing them. To en-
able detection of a wider range of cyber attacks, there
are methods of extending the capabilities of SIEM(I.
Kotenko and A. Chechulin, 2012; B. D. Bryant and H.
Saiedian, 2017). These methods can detect cyber at-
tacks, but depend on the skills of the administrators in
terms of response. As mentioned in Section 1, attack
detection alone is insufficient because of the variation
in skills among site administrators, and it is desirable
to provide response support as well.
There have been several systems proposed fo-
cused on information sharing within an organization,
such as our conventional system (M. Colajanni, D.
Gozzi, and M.Marchetti, 2008; C. Wagner, A. Du-
launoy, G. Wagener, and A. Iklody, 2016). The pur-
pose of these systems is to share threat information
within an organization. However, they share the mal-
ware information collected by honey pots or threat in-
formation collected by the administrators themselves.
If administrators lack skills, they may not be able to
effectively use the shared information well or col-
lect information to register in the system. Our con-
ventional system solves these problems by collecting
threat information itself and sharing countermeasure
recommendations instead of threat information.
Our proposed system focuses on the attack stages
of a cyber attack to evaluate the similarity of inci-
dents more accurately. Our conventional system uses
this similarity to make recommendations to site ad-
ministrators and enables early resolution of incidents.
Many studies have been conducted to mitigate dam-
age and resolve incidents early by focusing on the at-
tack stages. Pivarn
´
ıkov
´
a et al. propose a method for
detecting cyber attacks in their early stage and pre-
dicting how the attacks proceed by using Bayesian
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