« Newly Observed Elastic Defend Behavior Alert Node.js Pre or Post-Install Script Execution »
Elastic Docs ›Elastic Security [8.19] ›Detections and alerts ›Prebuilt rule reference

Newly Observed High Severity Detection Alert

edit
IMPORTANT: This documentation is no longer updated. Refer to Elastic's version policy and the latest documentation.

Newly Observed High Severity Detection Alert

edit

This rule detects Elastic SIEM high severity detection alerts that are observed for the first time in the previous 5 days of alert history. It highlights low-volume, newly observed alerts tied to a specific detection rule, analysts can use this to prioritize triage and response.

Rule type: esql

Rule indices: None

Severity: high

Risk score: 73

Runs every: 5m

Searches indices from: now-7205m (Date Math format, see also Additional look-back time)

Maximum alerts per execution: 100

References:

Tags:

  • Use Case: Threat Detection
  • Rule Type: Higher-Order Rule
  • Resources: Investigation Guide

Version: 2

Rule authors:

  • Elastic

Rule license: Elastic License v2

Investigation guide

edit

Triage and analysis

Investigating Newly Observed High Severity Detection Alert

This rule surfaces newly observed, low-frequency behavior high severity alerts affecting a single agent within the current day.

Because the alert has not been seen previously for this rule and host, it should be prioritized for validation to determine whether it represents a true compromise or rare benign activity.

Investigation Steps

  • Identify the affected host, user and review the associated rule name to understand the behavior that triggered the alert.
  • Validate the user context under which the activity occurred and assess whether it aligns with normal behavior for that account.
  • Refer to the specific rule investiguation guide for further actions.

False Positive Considerations

  • Newly deployed or updated software may introduce behavior not previously observed on the host.
  • Administrative scripts or automation tools can trigger behavior-based detections when first introduced.
  • Security tooling, IT management agents, or EDR integrations may generate new behavior alerts during updates or configuration changes.
  • Development or testing environments may produce one-off behaviors that resemble malicious techniques.

Response and Remediation

  • If the activity is confirmed malicious, isolate the affected host to prevent further execution or lateral movement.
  • Terminate malicious processes and remove any dropped files or persistence mechanisms.
  • Collect forensic artifacts to understand initial access and execution flow.
  • Patch or remediate any vulnerabilities or misconfigurations that enabled the behavior.
  • If benign, document the finding and consider tuning or exception handling to reduce future noise.
  • Continue monitoring the host and environment for recurrence of the behavior or related alerts.

Rule query

edit
FROM .alerts-security.*
| where kibana.alert.rule.name is not null and kibana.alert.risk_score >= 73  and
  not kibana.alert.rule.type in ("threat_match", "machine_learning", "new_terms") and
  not kibana.alert.rule.name like "Deprecated - *" and kibana.alert.rule.name != "My First Rule" and
  // covered by 7306ce7d-5c90-4f42-aa6c-12b0dc2fe3b8
  event.dataset != "endpoint.alerts"
| STATS Esql.alerts_count = count(*),
        Esql.first_time_seen = MIN(@timestamp),
        Esql.last_time_seen = MAX(@timestamp),
        Esql.process_executable = VALUES(process.executable),
        Esql.cmd_line = VALUES(process.command_line),
        Esql.parent_executable = VALUES(process.parent.executable),
        Esql.file_path_values = VALUES(file.path),
        Esql.file_path_values = VALUES(file.path),
        Esql.dll_path_values = VALUES(dll.path),
        Esql.user_id_values = VALUES(user.id),
        Esql.user_name_values = VALUES(user.name),
        Esql.agent_id_values = VALUES(agent.id),
        Esql.host_id_values = VALUES(host.id),
        Esql.event_module_values = VALUES(event.module),
        Esql.source_ip_values = VALUES(source.ip),
        Esql.agents_distinct_count = COUNT_DISTINCT(agent.id) by kibana.alert.rule.name
// fist time seen in the last 5 days - defined in the rule schedule Additional look-back time
| eval Esql.recent = DATE_DIFF("minute", Esql.first_time_seen, now())
// first time seen is within 10m of the rule execution time
| where Esql.recent <= 10 and Esql.agents_distinct_count == 1 and Esql.alerts_count <= 10 and (Esql.last_time_seen == Esql.first_time_seen)
| keep kibana.alert.rule.name, Esql.*
« Newly Observed Elastic Defend Behavior Alert Node.js Pre or Post-Install Script Execution »