Host risk scoreedit

This feature is available for Elastic Stack versions 7.16.0 and newer and requires a Platinum subscription or higher.

The host risk score feature highlights risky hosts from within your environment. It utilizes a transform with a scripted metric aggregation to calculate host risk scores based on alerts that were generated within the past five days. The transform runs hourly to update the score as new alerts are generated.

Each rule’s contribution to the host risk score is based on the rule’s risk score (signal.rule.risk_score) and a time decay factor to reduce the impact of stale alerts. The risk score is calculated using a weighted sum where rules with higher time-corrected risk scores also have higher weights. Each host risk score is normalized on a scale of 0 to 100.

Specific host attributes can boost the final risk score. For example, alert activity on a server poses a greater risk than that on a laptop. Therefore, the host risk score is 1.5 times higher if the host is a server. This boosted score is finalized after calculating the weighted sum of the time-corrected risks.

The following table shows how risk levels are applied to a host, based on the normalized risk score:

Risk level Host risk score

Unknown

< 20

Low

20-40

Moderate

40-70

High

70-90

Critical

> 90

Enable host risk scoreedit

To enable the host risk score feature, you must have alerts in your environment. If you previously enabled host risk score and are upgrading the Elastic Stack to 8.5 or newer, refer to Upgrade host risk score.

You can enable host risk score from the following places in the Elastic Security app:

  • The Entity Analytics dashboard
  • The Host risk tab on the Hosts page
  • The Host risk tab on a host’s details page

Or, in Kibana, you can enable host risk score in Console.

To enable host risk score from the Entity Analytics dashboard:

  1. In the Elastic Security app, go to DashboardsEntity Analytics.
  2. In the Host Risk Scores section, click Enable to install the module.

To enable host risk score from the Hosts page:

  1. Go to ExploreHosts.
  2. Select the Host risk tab, then click Enable to install the module.
Enable Host Risk Score button

To enable host risk score from a host’s details page:

  1. Go to ExploreHosts.
  2. Select the All hosts tab, then click a host name.
  3. On the details page, scroll down to the data tables, then select the Host risk tab.
  4. Click Enable to install the module.
Enable host risk score from the host’s details page

To enable host risk score from Console in Kibana, open a browser window and enter the following URL:

{KibanaURL}/s/{spaceID}/app/dev_tools#/console?load_from={KibanaURL}/s/{spaceID}/internal/risk_score/prebuilt_content/dev_tool/enable_host_risk_score

If there’s existing content in Console, scroll to the bottom to find the output loaded.

Upgrade host risk scoreedit

If you previously enabled host risk score and are upgrading to Elastic Stack version 8.5 or later, there’ll be an Upgrade button for host risk score instead of Enable.

Before upgrading, note the following:

  • Since older data is not preserved, previous host risk scores will be deleted, and new scores will be created. However, if you want to retain old host risk scores, you can reindex them before upgrading. To learn how, refer to Reindex API. New data will be stored in the ml_host_risk_score_<space-id> and ml_host_risk_score_latest_<space-id> indices.
  • You must edit your Kibana user settings and remove the xpack.securitySolution.enableExperimental:['riskyHostsEnabled'] feature flag.

After this is done, you can proceed with upgrading the host risk score feature from any of the following places in the Elastic Security app:

  • The Entity Analytics dashboard
  • The Host risk tab on the Hosts page
  • The Host risk tab on a host’s details page

After you enable or upgrade host risk score, you might get a message that says, "No host risk score data available to display." To verify that the transform that installs the host risk score module is picking up data, refer to Verify that host risk score data installed successfully.

Analyze host risk score dataedit

It is recommended you analyze hosts with the highest risk scores first — those in the Critical and Moderate categories. Host risk score data appears in the following places in the Elastic Security app:

The host.risk.calculated_level column in the Alerts table:

Host risk score in the Alerts table

The Overview tab on the Alert details flyout:

Host risk score in Alert details flyout

The Host risk classification column in the All hosts table on the Hosts page:

Host risk score on the Hosts page

The Host risk tab on the Hosts page:

Host risk score on the host details page

The Overview section on the host details page:

Host risk score in Overview section

The Host risk tab on the host details page:

Host risk score on the Hosts risk tab

You can also visualize host risk score data using prebuilt dashboards that are automatically imported when the feature is enabled.

To access the dashboards:

  1. In Kibana, go to AnalyticsDashboard, then search for risk score.
  2. Select Drilldown of Host Risk Score to analyze the risk components of a host, or Current Risk Score for Hosts to display a list of current risky hosts in your environment.
Select host risk score dashboard

In this example, we’ll explore the Drilldown of Host Risk Score dashboard.

Shows dashboard

Use the histogram to track how the risk score for a particular host has changed over time. To specify a date range, use the date and time picker, or drag and select a time range within the histogram.

histogram

To go to the host’s details page, click any host’s corresponding bar in the histogram, then select Go to Host View.

go to host view

The histogram shows historical changes in a particular host’s risk score(s). To specify a date range, use the date and time picker, or drag and select a time range within the histogram.

data tables