Terrance DeJesus
115 lines
4.1 KiB
TOML
115 lines
4.1 KiB
TOML
[metadata]
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creation_date = "2022/07/03"
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integration = ["endpoint"]
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maturity = "production"
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updated_date = "2024/08/08"
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[rule]
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author = ["Elastic"]
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description = """
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Identifies the execution of a browser process to open an HTML file with high entropy and size. Adversaries may smuggle
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data and files past content filters by hiding malicious payloads inside of seemingly benign HTML files.
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"""
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from = "now-9m"
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index = ["logs-endpoint.events.process-*", "logs-endpoint.events.file-*"]
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language = "eql"
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license = "Elastic License v2"
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name = "Suspicious HTML File Creation"
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note = "This rule may have a low to medium performance impact due variety of file paths potentially matching each EQL sequence."
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risk_score = 47
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rule_id = "f0493cb4-9b15-43a9-9359-68c23a7f2cf3"
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setup = """## Setup
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If enabling an EQL rule on a non-elastic-agent index (such as beats) for versions <8.2,
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events will not define `event.ingested` and default fallback for EQL rules was not added until version 8.2.
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Hence for this rule to work effectively, users will need to add a custom ingest pipeline to populate
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`event.ingested` to @timestamp.
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For more details on adding a custom ingest pipeline refer - https://www.elastic.co/guide/en/fleet/current/data-streams-pipeline-tutorial.html
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"""
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severity = "medium"
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tags = [
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"Domain: Endpoint",
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"OS: Windows",
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"Use Case: Threat Detection",
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"Tactic: Initial Access",
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"Data Source: Elastic Defend",
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]
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type = "eql"
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query = '''
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sequence by user.id with maxspan=2m
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[file where host.os.type == "windows" and event.action in ("creation", "rename") and
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/* Check for HTML files with high entropy and size */
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file.extension : ("htm", "html") and ((file.Ext.entropy >= 5 and file.size >= 150000) or file.size >= 1000000) and
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/* Check for file paths in common download and temporary directories */
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file.path : (
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"?:\\Users\\*\\Downloads\\*",
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"?:\\Users\\*\\Content.Outlook\\*",
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"?:\\Users\\*\\AppData\\Local\\Temp\\Temp?_*",
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"?:\\Users\\*\\AppData\\Local\\Temp\\7z*",
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"?:\\Users\\*\\AppData\\Local\\Temp\\Rar$*")]
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[process where host.os.type == "windows" and event.action == "start" and
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(
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/* Check for browser processes opening HTML files with single argument */
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(process.name in ("chrome.exe", "msedge.exe", "brave.exe", "whale.exe", "browser.exe", "dragon.exe", "vivaldi.exe", "opera.exe")
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and process.args == "--single-argument") or
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/* Optionally, check for browser processes opening HTML files with two arguments */
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(process.name == "iexplore.exe" and process.args_count == 2) or
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/* Optionally, check for browser processes opening HTML files with URL argument */
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(process.name in ("firefox.exe", "waterfox.exe") and process.args == "-url")
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)
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/* Check for file paths in common download and temporary directories targeted in the process arguments */
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and process.args : ("?:\\Users\\*\\Downloads\\*.htm*",
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"?:\\Users\\*\\Content.Outlook\\*.htm*",
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"?:\\Users\\*\\AppData\\Local\\Temp\\Temp?_*.htm*",
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"?:\\Users\\*\\AppData\\Local\\Temp\\7z*.htm*",
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"?:\\Users\\*\\AppData\\Local\\Temp\\Rar$*.htm*")]
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'''
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[[rule.threat]]
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framework = "MITRE ATT&CK"
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[[rule.threat.technique]]
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id = "T1566"
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name = "Phishing"
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reference = "https://attack.mitre.org/techniques/T1566/"
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[[rule.threat.technique.subtechnique]]
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id = "T1566.001"
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name = "Spearphishing Attachment"
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reference = "https://attack.mitre.org/techniques/T1566/001/"
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[[rule.threat.technique.subtechnique]]
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id = "T1566.002"
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name = "Spearphishing Link"
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reference = "https://attack.mitre.org/techniques/T1566/002/"
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[rule.threat.tactic]
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id = "TA0001"
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name = "Initial Access"
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reference = "https://attack.mitre.org/tactics/TA0001/"
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[[rule.threat]]
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framework = "MITRE ATT&CK"
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[[rule.threat.technique]]
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id = "T1027"
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name = "Obfuscated Files or Information"
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reference = "https://attack.mitre.org/techniques/T1027/"
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[[rule.threat.technique.subtechnique]]
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id = "T1027.006"
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name = "HTML Smuggling"
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reference = "https://attack.mitre.org/techniques/T1027/006/"
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[rule.threat.tactic]
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id = "TA0005"
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name = "Defense Evasion"
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reference = "https://attack.mitre.org/tactics/TA0005/"
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