sigma-rules/rules/windows/privilege_escalation_thread_cpu_priority_hijack.toml

[metadata]
creation_date = "2025/09/25"
integration = ["system", "windows"]
maturity = "production"
updated_date = "2025/11/14"

[rule]
author = ["Elastic"]
description = """
Identifies attempts to use the SeIncreaseBasePriorityPrivilege privilege by an unusual process. This could be related to
hijack execution flow of a process via threats priority manipulation.
"""
from = "now-9m"
index = ["logs-system.security*", "logs-windows.forwarded*", "winlogbeat-*"]
language = "kuery"
license = "Elastic License v2"
name = "Suspicious SeIncreaseBasePriorityPrivilege Use"
note = """## Triage and analysis

### Investigating Suspicious SeIncreaseBasePriorityPrivilege Use

SeIncreaseBasePriorityPrivilege allows to increase the priority of processes running on the system so that the CPU scheduler allows them to pre-empt other lower priority processes when the higher priority process has something to do.

### Possible investigation steps

- Review the process.executable reputation and it's execution chain.
- Investiguate if the SubjectUserName is expected to perform this action.
- Correlate the event with other security alerts or logs to identify any patterns or additional suspicious activities that might suggest a broader attack campaign.
- Check the agent health status and verify if there is any tampering with endpoint security processes.

### False positive analysis

- Administrative tasks involving legitimate CPU scheduling priority changes.

### Response and remediation

- Immediately isolate the affected machine from the network to prevent further unauthorized access or lateral movement within the domain.
- Terminate the processes involved in the execution chain.
- Escalate the incident to the security operations center (SOC) or incident response team for further investigation and to ensure comprehensive remediation efforts are undertaken."""
references = [
    "https://github.com/Octoberfest7/ThreadCPUAssignment_POC/tree/main",
    "https://x.com/sixtyvividtails/status/1970721197617717483",
    "https://learn.microsoft.com/en-us/previous-versions/windows/it-pro/windows-10/security/threat-protection/auditing/event-4674"
]
risk_score = 73
rule_id = "6fa0f15b-1926-419b-8de2-fce1429797ba"
setup = """## Setup

Ensure advanced audit policies for Windows are enabled, specifically:
Audit Sensitive Privilege Use [Event ID 4674](https://learn.microsoft.com/en-us/previous-versions/windows/it-pro/windows-10/security/threat-protection/auditing/event-4674) (An operation was attempted on a privileged object.)

```
Computer Configuration >
Policies >
Windows Settings >
Security Settings >
Advanced Audit Policies Configuration >
Audit Policies >
Privilege Use >
Audit Sensitive Privilege Use (Success)
```
"""
severity = "high"
tags = [
    "Domain: Endpoint",
    "OS: Windows",
    "Use Case: Threat Detection",
    "Tactic: Privilege Escalation",
    "Data Source: Windows Security Event Logs",
    "Resources: Investigation Guide",
]
timestamp_override = "event.ingested"
type = "query"

query = '''
event.category:iam and host.os.type:"windows" and event.code:"4674" and
winlog.event_data.PrivilegeList:"SeIncreaseBasePriorityPrivilege" and event.outcome:"success" and
winlog.event_data.AccessMask:"512" and not winlog.event_data.SubjectUserSid:("S-1-5-18" or "S-1-5-19" or "S-1-5-20")
'''


[[rule.threat]]
framework = "MITRE ATT&CK"
[[rule.threat.technique]]
id = "T1134"
name = "Access Token Manipulation"
reference = "https://attack.mitre.org/techniques/T1134/"


[rule.threat.tactic]
id = "TA0004"
name = "Privilege Escalation"
reference = "https://attack.mitre.org/tactics/TA0004/"