Multiple Alerts on a Host Exhibiting CPU Spike

[metadata]
creation_date = "2026/01/26"
maturity = "production"
updated_date = "2026/02/26"

[rule]
author = ["Elastic"]
description = """
This rule correlates multiple security alerts from a host exhibiting unusually high CPU utilization within a short time window.
This behavior may indicate malicious activity such as malware execution, cryptomining, exploit payload execution,
or abuse of system resources following initial compromise.
"""
from = "now-9m"
interval = "5m"
language = "esql"
license = "Elastic License v2"
name = "Multiple Alerts on a Host Exhibiting CPU Spike"
setup = """## Setup

This rule requires host CPU metrics collected via the Elastic Agent **System** integration.

### System Metrics Integration Setup
The System integration collects host-level metrics such as CPU usage, load, memory, and process statistics and sends them to Elasticsearch using Elastic Agent.

#### Prerequisite Requirements:
- Elastic Agent managed by Fleet
- A Fleet Server configured and reachable
  Refer to the Fleet Server setup guide:
  https://www.elastic.co/guide/en/fleet/current/fleet-server.html

#### The following steps should be executed in order to enable CPU metrics collection:
- Go to the Kibana home page and click **Add integrations**.
- In the search bar, enter **System** and select the **System** integration.
- Click **Add System**.
- Configure an integration name and optionally add a description.
- Under **Metrics**, ensure the following datasets are enabled:
  - `system.cpu`
  - `system.load` (optional but recommended)
  - `system.process` (optional, if process-level CPU is required)
- Review optional and advanced settings as needed.
- Add the integration to an existing agent policy or create a new agent policy.
- Deploy the Elastic Agent to the hosts from which CPU metrics should be collected.
- Click **Save and Continue** to finalize the setup.

#### Validation
After deployment, verify CPU metrics ingestion by confirming the presence of documents in:
- `metrics-system.cpu-*`
- `metrics-system.load-*` (if enabled)

For more details on the System integration and available metrics, refer to the documentation:
https://docs.elastic.co/integrations/system
"""
risk_score = 99
rule_id = "b7f77c3c-1bcb-4afc-9ace-49357007947b"
severity = "critical"
tags = [
    "Use Case: Threat Detection",
    "Rule Type: Higher-Order Rule",
    "Resources: Investigation Guide",
    "Domain: Endpoint",
    "Tactic: Impact"
]
timestamp_override = "event.ingested"
type = "esql"

query = '''
FROM metrics-*, .alerts-security.*  METADATA _index
| where not KQL("""kibana.alert.rule.tags : "Rule Type: Higher-Order Rule" """)
| eval
       // hosts with more than 90% total CPU use
       cpu_metrics_host_ids = CASE(_index like ".ds-metrics-system.cpu-*" and system.cpu.total.norm.pct >= 0.9, host.id, null),
       // hosts with high severity security alerts
       alerts_host_ids = CASE(_index like ".internal.alerts-security.*" and kibana.alert.rule.name is not null and host.id is not null and kibana.alert.risk_score >= 73, host.id, null)
| stats host_with_cpu_spike = COUNT_DISTINCT(cpu_metrics_host_ids),
        host_with_alerts = COUNT_DISTINCT(alerts_host_ids),
        Esql.max_cpu_pct = MAX(system.cpu.total.norm.pct),
        Esql.unique_alerts_count = COUNT_DISTINCT(kibana.alert.rule.name),
        Esql.unique_process_count = COUNT_DISTINCT(process.entity_id),
        Esql.alerts = VALUES(kibana.alert.rule.name),
        Esql.process_hash_sha256 = VALUES(process.hash.sha256),
        process_path = VALUES(process.executable),
        parent_process_path = VALUES(process.parent.executable),
        user_name = VALUES(user.name),
        host_name = VALUES(host.name),
        cmdline = VALUES(process.command_line) by host.id
// at least 3 unique high severity alerts and from a host with 90% CPU use
| where host_with_cpu_spike > 0 and host_with_alerts > 0 and Esql.unique_alerts_count >= 3
| eval process.hash.sha256 = MV_FIRST(Esql.process_hash_sha256),
       process.executable = MV_FIRST(process_path),
       process.parent.executable = MV_FIRST(parent_process_path),
       process.command_line = MV_FIRST(cmdline),
       host.name = MV_FIRST(host_name),
       user.name = MV_FIRST(user_name)
| KEEP user.name, host.name, host.id, process.*, Esql.*
'''
note = """## Triage and analysis

### Investigating Multiple Alerts on a Host Exhibiting CPU Spike

This rule identifies hosts that both triggered multiple security alerts and exhibited unusually high CPU utilization on the
within a short time window. This combination may indicate malicious execution, resource abuse, or post-compromise activity.

### Possible investigation steps
- Review the correlated alert(s) to understand why the host was flagged by the detection alerts.
- Examine the involved process name, command line, and SHA-256 hash to determine whether those processes are expected or known to be malicious.
- Validate the observed CPU usage and duration to determine whether the spike is abnormal for this process and host.
- Check for related process activity such as parent/child processes, suspicious process spawning, or privilege escalation attempts.
- Review additional host telemetry including:
  - Network connections initiated by the process
  - File creation or modification events
  - Persistence mechanisms (services, scheduled tasks, registry keys)
- Determine whether similar activity is observed on other hosts, which may indicate a broader compromise.

### False positive analysis
- Legitimate high-CPU processes such as software updates, backup agents, security scans, or system maintenance tasks.
- Resource-intensive but benign applications (e.g., compilers, video encoding, data processing jobs).
- Security tools or monitoring agents temporarily consuming high CPU.

### Response and remediation
- If malicious activity is confirmed, isolate the affected host to prevent further impact.
- Terminate the offending process if safe to do so.
- Remove any identified malicious binaries or artifacts and eliminate persistence mechanisms.
- Apply relevant patches or configuration changes to remediate the root cause.
- Monitor the environment for recurrence of similar high-CPU processes combined with security alerts.
- Escalate the incident if multiple hosts or indicators suggest coordinated or widespread activity."""

[[rule.threat]]
framework = "MITRE ATT&CK"

[rule.threat.tactic]
id = "TA0040"
name = "Impact"
reference = "https://attack.mitre.org/tactics/TA0040/"