sigma-rules/rules/linux/execution_process_started_from_process_id_file.toml

[metadata]
creation_date = "2022/05/11"
integration = ["endpoint"]
maturity = "production"
min_stack_comments = "New fields added: required_fields, related_integrations, setup"
min_stack_version = "8.3.0"
updated_date = "2023/06/22"

[rule]
author = ["Elastic"]
description = """
Identifies a new process starting from a process ID (PID), lock or reboot file within the temporary file storage
paradigm (tmpfs) directory /var/run directory. On Linux, the PID files typically hold the process ID to track previous
copies running and manage other tasks. Certain Linux malware use the /var/run directory for holding data, executables
and other tasks, disguising itself or these files as legitimate PID files.
"""
false_positives = [
    """
    False-Positives (FP) should be at a minimum with this detection as PID files are meant to hold process IDs, not
    inherently be executables that spawn processes.
    """,
]
from = "now-9m"
index = ["logs-endpoint.events.*", "endgame-*"]
language = "eql"
license = "Elastic License v2"
name = "Process Started from Process ID (PID) File"
note = """## Triage and analysis

### Investigating Process Started from Process ID (PID) File
Detection alerts from this rule indicate a process spawned from an executable masqueraded as a legitimate PID file which is very unusual and should not occur. Here are some possible avenues of investigation:
- Examine parent and child process relationships of the new process to determine if other processes are running.
- Examine the /var/run directory using Osquery to determine other potential PID files with unsually large file sizes, indicative of it being an executable: "SELECT f.size, f.uid, f.type, f.path from file f WHERE path like '/var/run/%%';"
- Examine the reputation of the SHA256 hash from the PID file in a database like VirusTotal to identify additional pivots and artifacts for investigation."""
references = [
    "https://www.sandflysecurity.com/blog/linux-file-masquerading-and-malicious-pids-sandfly-1-2-6-update/",
    "https://twitter.com/GossiTheDog/status/1522964028284411907",
    "https://exatrack.com/public/Tricephalic_Hellkeeper.pdf",
    "https://www.elastic.co/security-labs/a-peek-behind-the-bpfdoor",
]
risk_score = 73
rule_id = "3688577a-d196-11ec-90b0-f661ea17fbce"
severity = "high"
tags = ["Domain: Endpoint", "OS: Linux", "Use Case: Threat Detection", "Tactic: Execution", "Threat: BPFDoor", "Data Source: Elastic Endgame", "Data Source: Elastic Defend"]
timestamp_override = "event.ingested"
type = "eql"

query = '''
process where host.os.type == "linux" and event.type == "start" and user.id == "0" and
  process.executable regex~ """/var/run/\w+\.(pid|lock|reboot)"""
'''


[[rule.threat]]
framework = "MITRE ATT&CK"
[[rule.threat.technique]]
id = "T1059"
name = "Command and Scripting Interpreter"
reference = "https://attack.mitre.org/techniques/T1059/"


[rule.threat.tactic]
id = "TA0002"
name = "Execution"
reference = "https://attack.mitre.org/tactics/TA0002/"