Potential Common Log File System Exploit

Source: github.com/elastic/protections-artifacts

Identifies an unelevated attempt to create a BLF file using the Common Log File System (CLFS) API. This may indicate an attempt to exploit a CLFS vulnerability for privilege escalation.

MITRE ATT&CK coverage

Tactic	Techniques
Privilege Escalation	`T1068` Exploitation for Privilege Escalation

Rule body

[rule]
description = """
Identifies an unelevated attempt to create a BLF file using the Common Log File System (CLFS) API. This may indicate an
attempt to exploit a CLFS vulnerability for privilege escalation.
"""
id = "4fd4edfd-3bb4-4eac-82f2-8d4ebcbed0f3"
license = "Elastic License v2"
name = "Potential Common Log File System Exploit"
os_list = ["windows"]
reference = [
    "https://securelist.com/windows-clfs-exploits-ransomware/111560/",
    "https://www.elastic.co/security-labs/itw-windows-lpe-0days-insights-and-detection-strategies",
]
version = "1.0.3"

query = '''
file where event.action != "deletion" and user.id != "S-1-5-18" and user.id != null and process.pid != 4 and
  _arraysearch(process.thread.Ext.call_stack, $entry, $entry.symbol_info: ("*clfsw32.dll!CreateLogFile*", "*clfsw32.dll!AddLogContainerSet*"))
'''

min_endpoint_version = "8.7.0"
optional_actions = []
[[actions]]
action = "kill_process"
field = "process.entity_id"
state = 0
tree = true

[[threat]]
framework = "MITRE ATT&CK"
[[threat.technique]]
id = "T1068"
name = "Exploitation for Privilege Escalation"
reference = "https://attack.mitre.org/techniques/T1068/"


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

[internal]
min_endpoint_version = "8.7.0"

Stages and Predicates

Stage 1: `file`

file where event.action != "deletion" and user.id != "S-1-5-18" and user.id != null and process.pid != 4 and
  _arraysearch(process.thread.Ext.call_stack, $entry, $entry.symbol_info: ("*clfsw32.dll!CreateLogFile*", "*clfsw32.dll!AddLogContainerSet*"))

Indicators

These rows show field, operator, and value matches.