Information processing apparatus, information processing method, and computer readable medium

1. An information processing apparatus for detecting an attacked on one or more monitored target computing apparatuses, the information processing apparatus comprising:

a memory configured to store, for a plurality of events, event stage information describing an event, a pre-event stage, and a post-event stage, the event being observed by an information system when an attack against the information system is underway, the pre-event stage being a stage of a progress of an attack before the event is observed, the post-event stage being a stage of a progress of an attack after the event is observed; and

processing circuitry configured to

receive an observed event notice from one of the one or more monitored target computing apparatuses, the observed event notice including information notifying an observed event which is observed by the information system;

acquire corresponding event stage information describing the observed event received in the observed event notice information;

determine whether attack activity status information has been stored for the observed event;

create, in response to a determination that no attack activity status information has been stored for the observed event, new attack activity status information for the observed event based on the corresponding event stage information;

update, in response to a determination that attack activity status information has been stored for the observed event, an accumulated attack likelihood in the stored attack activity status information;

acquire the accumulated attack likelihood for the observed event from the attack activity status information corresponding to the observed event;

notify a user of an occurrence of an attack if the acquired accumulated attack likelihood is greater than a predefined value;

determine, if the acquired accumulated attack likelihood is less than or equal to the predefined value, a predicted observation event that can occur next by

acquiring a post-event stage of the observed event from the corresponding event stage information,

acquiring event stage information, including attack activity definition information, for an event corresponding to the acquired post-event stage that describes a pre-event stage corresponding to the acquired post-event stage of the observed event,

determining whether pre-event stage conditions of the acquired attack activity definition information have been satisfied, and

setting as the predicted observation event the event corresponding to the acquired post-event stage if the pre-event stage conditions have been satisfied.

2. The information processing apparatus according to claim 1 , wherein the processing circuitry is further configured to relate, when a new predicted observation event is determined based on the observed event, the updated accumulated attack likelihood to event stage information describing the new predicted observation event.

3. The information processing apparatus according to claim 1 , wherein the processing circuitry is further configured to notify a user of an occurrence of an attack by displaying a notice message notifying that an attack against the information system is underway.

4. The information processing apparatus according to claim 1 , wherein

the received observed event notice information includes a type of an observed event and a variable value specifying an observed event, and

each time the observed event notice information is received and a predicted observation event is determined, the processing circuitry is configured to

relate an accumulated attack likelihood and a variable value notified by observed event notice information to event stage information describing a predicted observation event,

acquire event stage information describing an event corresponding to a type of observed event notified by received observed event notice information, and

compare a variable value related to the acquired event stage information describing an event corresponding to a type of observed event with a variable value notified by observed event notice information, and

update, if the compared variable values are identical, accumulated attack likelihood.

5. The information processing apparatus according to claim 1 , wherein the processing circuitry is further configured to

store event stage information describing a monitoring operation start threshold to cause a device included in the information system to start a predetermined monitoring operation, and

cause, if the updated accumulated attack likelihood exceeds the monitoring operation start threshold, the device included in the information system to start the monitoring operation.

6. The information processing apparatus according to claim 1 , wherein the processing circuitry determines whether or not the pre-event stage conditions of the acquired attack activity definition information have been satisfied by referring to inference rule information that describes an inference logic.

7. The information processing apparatus according to claim 1 , wherein the processing circuitry determines whether the pre-event stage conditions of the acquired attack activity definition information have been satisfied by referring to configuration information that describes a configuration of the information system.

8. The information processing apparatus according to claim 1 , wherein the processing circuitry stores event stage information using a predicate logic.

9. The information processing apparatus according to claim 1 , wherein event stage information includes a process practice identifier indicating that a process of determining the predicted observation event is practiced even if a pre-event stage is unsatisfied for any one event, and

the processing circuitry is configured to

acquire, even if a pre-event stage described in acquired event stage information is unsatisfied, the post-event stage of the observed event,

acquire the event stage information describing the pre-event stage corresponding to the acquired post-event stage of the observed event, and

determine the predicted observation event based on the acquired event stage information describing the pre-event stage, and

when the acquired event stage information describing the pre-event stage does not describe a process practice identifier, if a pre-event stage described in the acquired event stage information describing the pre-event stage is unsatisfied, does not determine a predicted observation event.

10. The information processing apparatus according to claim 1 , wherein the information system accumulates event derivation information capable of deriving an event, including an event in the information system which is not notified by the observed event notice information, and

wherein the processing circuitry is further configured to

acquire event stage information describing the observed event notified by the observed event notice information received,

determine whether or not a pre-event stage described in acquired event stage information is satisfied based on the event derivation information accumulated in the information system, and

if the pre-event stage is satisfied, acquire the post-event stage of the observed event from acquired event stage information, acquire event stage information describing a pre-event stage corresponding to the acquired post-event stage of the observed event, and extract the predicted observation event.

11. The information processing apparatus according to claim 10 , wherein event stage information includes an attack likelihood value indicating a likelihood of an attack against the information system when an event is observed, and

as a result of determining whether or not the pre-event stage is satisfied based on the event derivation information accumulated in the information system, if the pre-event stage is satisfied, the processing circuitry is configured to

analyze the event derivation information accumulated in the information system and select at least one event stage information from among a plurality of pieces of stored event stage information stored, and

accumulate an attack likelihood value described in the selected event stage information and an attack likelihood value, to obtain an accumulated value of an attack likelihood value.

12. The information processing apparatus according to claim 1 , wherein the processing circuitry is further configured to determine the accumulated attack likelihood based on a reception frequency of how often the observed event notice information is received.

13. The information processing apparatus according to claim 7 , wherein the processing circuitry is further configured to collect the configuration information from the information system.

14. An information processing method for detecting an attack on one or more monitored target computing apparatuses performed by a computer that stores, for a plurality of events, event stage information describing an event, a pre-event stage, and a post-event stage, the event being observed by an information system when an attack against the information system is underway, the pre-event stage being a stage of a progress of an attack before the event is observed, the post-event stage being a stage of a progress of an attack after the event is observed, the information processing method comprising:

receiving an observed event notice from one or more of the one or more monitored target computing apparatuses, the observed event notice including information notifying an observed event which is observed by the information system;

acquiring corresponding event stage information describing the observed event received in the observed event notice information;

determining whether attack activity status information has been stored for the observed event,

creating, in response to a determination that no attack activity status information has been stored for the observed event, new attack activity status information for the observed event based on the corresponding event stage information;

updating, in response to a determination that attack activity status information has been stored for the observed event, an accumulated attack likelihood in the stored attack activity status information;

acquiring the accumulated attack likelihood for the observed event from the attack activity status information corresponding to the observed event;

notifying a user of an occurrence of an attack if the acquired accumulated attack likelihood is greater than a predefined value;

determining, if the acquired accumulated attack likelihood is less than or equal to the predefined value, a predicted observation event that can occur next by

acquiring a post-event stage of the observed event from the corresponding event stage information,

acquiring event stage information, including attack activity definition information, for an event corresponding to the acquired post-event stage that describes a pre-event stage corresponding to the acquired post-event stage of the observed event,

determining whether pre-event stage conditions of the acquired attack activity definition information have been satisfied, and

setting as the predicted observation event the event corresponding to the acquired post-event stage if the pre-event stage conditions have been satisfied.

15. A non-transitory computer readable medium storing a program to cause a computer that stores, for a plurality of events, event stage information describing an event, a pre-event stage, and a post-event stage, the event being observed by an information system when an attack against the information system is underway, the pre-event stage being a stage of a progress of an attack before the event is observed, the post-event stage being a stage of a progress of an attack after the event is observed, to execute a process for detecting an attack on one or more monitored target apparatuses that comprises:

receiving an observed event notice from one of the one or more monitored target apparatuses, the observed event notice including information notifying an observed event which is observed by the information system;

acquiring corresponding event stage information describing the observed event received in the observed event notice information;

determining whether attack activity status information has been stored for the observed event;

creating, in response to a determination that no attack activity status information has been stored for the observed event, new attack activity status information for the observed event based on the corresponding event stage information;

updating, in response to a determination that attack activity status information has been stored for the observed event, an accumulated attack likelihood in the stored attack activity status information;

acquiring the accumulated attack likelihood for the observed event from the attack activity status information corresponding to the observed event;

notifying a user of an occurrence of an attack if the acquired accumulated attack likelihood is greater than a predefined value;

determining, if the acquired accumulated attack likelihood is less than or equal to the predefined value, a predicted observation event that can occur next by

acquiring a post-event stage of the observed event from the corresponding event stage information,

acquiring event stage information, including attack activity definition information, for an event corresponding to the acquired post-event stage that describes a pre-event stage corresponding to the acquired post-event stage of the observed event,

determining whether pre-event stage conditions of the acquired attack activity definition information have been satisfied, and

setting as the predicted observation event the event corresponding to the acquired post-event stage if the pre-event stage conditions have been satisfied.