[metadata]
creation_date = "2023/03/20"
integration = ["endpoint"]
maturity = "production"
min_stack_comments = "New fields added: required_fields, related_integrations, setup"
min_stack_version = "8.3.0"
updated_date = "2023/06/15"

[rule]
author = ["Elastic"]
description = """
This rule identifies a sequence of a mass file encryption event in conjunction with the creation of a .txt file with 
a file name containing ransomware keywords executed by the same process in a 1 second timespan. Ransomware is a type of
malware that encrypts a victim's files or systems and demands payment (usually in cryptocurrency) in exchange for the
decryption key. One important indicator of a ransomware attack is the mass encryption of the file system, after which a
new file extension is added to the file. 
"""
from = "now-9m"
index = ["logs-endpoint.events.*"]
language = "eql"
license = "Elastic License v2"
name = "Potential Linux Ransomware Note Creation Detected"
risk_score = 73
rule_id = "c8935a8b-634a-4449-98f7-bb24d3b2c0af"
severity = "high"
tags = ["Domain: Endpoint", "OS: Linux", "Use Case: Threat Detection", "Tactic: Impact"]
type = "eql"
query = '''
sequence by host.id, process.entity_id with maxspan=1s 
  [ file where host.os.type == "linux" and event.type == "change" and
    event.action == "rename" and file.extension != "" and 
    file.path : (
      "/home/*", "/etc/*", "/root/*", "/opt/*", "/var/backups/*", "/var/lib/log/*"
      ) and not 
    file.extension : (
      "xml", "json", "conf", "dat", "gz", "info", "mod", "final",
      "php", "pyc", "log", "bak", "bin", "csv", "pdf", "cfg", "*old"
      ) and not 
    process.name : (
      "dpkg",  "yum", "dnf", "rpm", "dockerd"
      ) ] with runs=100
  [ file where host.os.type == "linux" and event.action == "creation" and file.extension == "txt" and 
    file.name : (
      "*crypt*", "*restore*", "*lock*", "*recovery*", "*data*", 
      "*read*", "*instruction*", "*how_to*", "*ransom*"
      ) ] | tail 1
'''


[[rule.threat]]
framework = "MITRE ATT&CK"
[[rule.threat.technique]]
id = "T1486"
name = "Data Encrypted for Impact"
reference = "https://attack.mitre.org/techniques/T1486/"


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