File Creation in /var/log via Suspicious Process

  1[metadata]
  2creation_date = "2025/03/11"
  3integration = ["endpoint", "sentinel_one_cloud_funnel"]
  4maturity = "production"
  5min_stack_comments = "Breaking change at 8.13.0 for SentinelOne Integration."
  6min_stack_version = "8.13.0"
  7updated_date = "2025/03/11"
  8
  9[rule]
 10author = ["Elastic"]
 11description = """
 12This rule detects the creation of files in the /var/log/ directory via process executables located in
 13world-writeable locations or via hidden processes. Attackers may attempt to hide their activities by
 14creating files in the /var/log/ directory, which is commonly used for logging system events. 
 15"""
 16from = "now-9m"
 17index = ["logs-endpoint.events.file*", "logs-sentinel_one_cloud_funnel.*", "endgame-*"]
 18language = "kuery"
 19license = "Elastic License v2"
 20name = "File Creation in /var/log via Suspicious Process"
 21risk_score = 21
 22rule_id = "ddf26e25-3e30-42b2-92db-bde8eb82ad67"
 23setup = """## Setup
 24
 25This rule requires data coming in from Elastic Defend.
 26
 27### Elastic Defend Integration Setup
 28Elastic Defend is integrated into the Elastic Agent using Fleet. Upon configuration, the integration allows the Elastic Agent to monitor events on your host and send data to the Elastic Security app.
 29
 30#### Prerequisite Requirements:
 31- Fleet is required for Elastic Defend.
 32- To configure Fleet Server refer to the [documentation](https://www.elastic.co/guide/en/fleet/current/fleet-server.html).
 33
 34#### The following steps should be executed in order to add the Elastic Defend integration on a Linux System:
 35- Go to the Kibana home page and click "Add integrations".
 36- In the query bar, search for "Elastic Defend" and select the integration to see more details about it.
 37- Click "Add Elastic Defend".
 38- Configure the integration name and optionally add a description.
 39- Select the type of environment you want to protect, either "Traditional Endpoints" or "Cloud Workloads".
 40- Select a configuration preset. Each preset comes with different default settings for Elastic Agent, you can further customize these later by configuring the Elastic Defend integration policy. [Helper guide](https://www.elastic.co/guide/en/security/current/configure-endpoint-integration-policy.html).
 41- We suggest selecting "Complete EDR (Endpoint Detection and Response)" as a configuration setting, that provides "All events; all preventions"
 42- Enter a name for the agent policy in "New agent policy name". If other agent policies already exist, you can click the "Existing hosts" tab and select an existing policy instead.
 43For more details on Elastic Agent configuration settings, refer to the [helper guide](https://www.elastic.co/guide/en/fleet/8.10/agent-policy.html).
 44- Click "Save and Continue".
 45- To complete the integration, select "Add Elastic Agent to your hosts" and continue to the next section to install the Elastic Agent on your hosts.
 46For more details on Elastic Defend refer to the [helper guide](https://www.elastic.co/guide/en/security/current/install-endpoint.html).
 47"""
 48severity = "low"
 49tags = [
 50    "Domain: Endpoint",
 51    "OS: Linux",
 52    "Use Case: Threat Detection",
 53    "Tactic: Defense Evasion",
 54    "Tactic: Execution",
 55    "Tactic: Persistence",
 56    "Data Source: Elastic Defend",
 57    "Data Source: SentinelOne",
 58    "Data Source: Elastic Endgame",
 59]
 60timestamp_override = "event.ingested"
 61type = "new_terms"
 62query = '''
 63event.category:file and host.os.type:linux and event.action:(creation or file_create_event or file_rename_event or rename) and
 64(process.executable:(/tmp/* or /var/tmp/* or /dev/shm/* or ./* or /boot/*) or process.name:.*) and
 65file.path:/var/log/* and not file.extension:*
 66'''
 67
 68[[rule.threat]]
 69framework = "MITRE ATT&CK"
 70
 71[[rule.threat.technique]]
 72id = "T1564"
 73name = "Hide Artifacts"
 74reference = "https://attack.mitre.org/techniques/T1564/"
 75
 76[[rule.threat.technique.subtechnique]]
 77id = "T1564.001"
 78name = "Hidden Files and Directories"
 79reference = "https://attack.mitre.org/techniques/T1564/001/"
 80
 81[rule.threat.tactic]
 82id = "TA0005"
 83name = "Defense Evasion"
 84reference = "https://attack.mitre.org/tactics/TA0005/"
 85
 86[[rule.threat]]
 87framework = "MITRE ATT&CK"
 88
 89[rule.threat.tactic]
 90name = "Execution"
 91id = "TA0002"
 92reference = "https://attack.mitre.org/tactics/TA0002/"
 93
 94[[rule.threat.technique]]
 95id = "T1059"
 96name = "Command and Scripting Interpreter"
 97reference = "https://attack.mitre.org/techniques/T1059/"
 98
 99[[rule.threat.technique.subtechnique]]
100name = "Unix Shell"
101id = "T1059.004"
102reference = "https://attack.mitre.org/techniques/T1059/004/"
103
104[[rule.threat]]
105framework = "MITRE ATT&CK"
106
107[rule.threat.tactic]
108id = "TA0003"
109name = "Persistence"
110reference = "https://attack.mitre.org/tactics/TA0003/"
111
112[rule.new_terms]
113field = "new_terms_fields"
114value = ["file.path", "process.executable"]
115
116[[rule.new_terms.history_window_start]]
117field = "history_window_start"
118value = "now-10d"