sigma-rules/rules/windows/defense_evasion_masquerading_communication_apps.toml

[metadata]
creation_date = "2023/05/05"
integration = ["endpoint"]
maturity = "production"
min_stack_comments = "New fields added: required_fields, related_integrations, setup"
min_stack_version = "8.3.0"
updated_date = "2023/10/13"

[rule]
author = ["Elastic"]
description = """
Identifies suspicious instances of communications apps, both unsigned and renamed ones, that can indicate an attempt to
conceal malicious activity, bypass security features such as allowlists, or trick users into executing malware.
"""
from = "now-9m"
index = ["logs-endpoint.events.*"]
language = "eql"
license = "Elastic License v2"
name = "Potential Masquerading as Communication Apps"
risk_score = 47
rule_id = "c9482bfa-a553-4226-8ea2-4959bd4f7923"
severity = "medium"
tags = ["Domain: Endpoint", "OS: Windows", "Use Case: Threat Detection", "Tactic: Defense Evasion", "Data Source: Elastic Defend"]
timestamp_override = "event.ingested"
type = "eql"

query = '''
process where host.os.type == "windows" and
  event.type == "start" and
  (
    /* Slack */
    (process.name : "slack.exe" and not
      (process.code_signature.subject_name in (
        "Slack Technologies, Inc.",
        "Slack Technologies, LLC"
       ) and process.code_signature.trusted == true)
    ) or

    /* WebEx */
    (process.name : "WebexHost.exe" and not
      (process.code_signature.subject_name in ("Cisco WebEx LLC", "Cisco Systems, Inc.") and process.code_signature.trusted == true)
    ) or

    /* Teams */
    (process.name : "Teams.exe" and not
      (process.code_signature.subject_name == "Microsoft Corporation" and process.code_signature.trusted == true)
    ) or

    /* Discord */
    (process.name : "Discord.exe" and not
      (process.code_signature.subject_name == "Discord Inc." and process.code_signature.trusted == true)
    ) or

    /* RocketChat */
    (process.name : "Rocket.Chat.exe" and not
      (process.code_signature.subject_name == "Rocket.Chat Technologies Corp." and process.code_signature.trusted == true)
    ) or

    /* Mattermost */
    (process.name : "Mattermost.exe" and not
      (process.code_signature.subject_name == "Mattermost, Inc." and process.code_signature.trusted == true)
    ) or

    /* WhatsApp */
    (process.name : "WhatsApp.exe" and not
      (process.code_signature.subject_name in (
        "WhatsApp LLC",
        "WhatsApp, Inc",
        "24803D75-212C-471A-BC57-9EF86AB91435"
       ) and process.code_signature.trusted == true)
    ) or

    /* Zoom */
    (process.name : "Zoom.exe" and not
      (process.code_signature.subject_name == "Zoom Video Communications, Inc." and process.code_signature.trusted == true)
    ) or

    /* Outlook */
    (process.name : "outlook.exe" and not
      (process.code_signature.subject_name == "Microsoft Corporation" and process.code_signature.trusted == true)
    ) or

    /* Thunderbird */
    (process.name : "thunderbird.exe" and not
      (process.code_signature.subject_name == "Mozilla Corporation" and process.code_signature.trusted == true)
    )
  )
'''


[[rule.threat]]
framework = "MITRE ATT&CK"
[[rule.threat.technique]]
id = "T1036"
name = "Masquerading"
reference = "https://attack.mitre.org/techniques/T1036/"

[[rule.threat.technique.subtechnique]]
id = "T1036.001"
name = "Invalid Code Signature"
reference = "https://attack.mitre.org/techniques/T1036/001/"

[[rule.threat.technique.subtechnique]]
id = "T1036.005"
name = "Match Legitimate Name or Location"
reference = "https://attack.mitre.org/techniques/T1036/005/"


[rule.threat.tactic]
id = "TA0005"
name = "Defense Evasion"
reference = "https://attack.mitre.org/tactics/TA0005/"


[[rule.threat]]
framework = "MITRE ATT&CK"
[[rule.threat.technique]]
id = "T1554"
name = "Compromise Client Software Binary"
reference = "https://attack.mitre.org/techniques/T1554/"

[rule.threat.tactic]
id = "TA0003"
name = "Persistence"
reference = "https://attack.mitre.org/tactics/TA0003/"