Monitor Email For Brand Abuse

SPLUNK detection rule by David Dorsey, Splunk · Apache-2.0

The following analytic identifies emails claiming to be sent from a domain similar to one you are monitoring for potential abuse. It leverages email header data, specifically the sender's address, and cross-references it with a lookup table of known domain permutations generated by the "ESCU - DNSTwist Domain Names" search. This activity is significant as it can indicate phishing attempts or brand impersonation, which are common tactics used in social engineering attacks. If confirmed malicious, this could lead to unauthorized access, data theft, or reputational damage.

name: Monitor Email For Brand Abuse
id: b2ea1f38-3a3e-4b8a-9cf1-82760d86a6b8
version: 11
creation_date: '2020-04-29'
modification_date: '2026-05-13'
author: David Dorsey, Splunk
status: experimental
type: TTP
description: The following analytic identifies emails claiming to be sent from a domain similar to one you are monitoring for potential abuse. It leverages email header data, specifically the sender's address, and cross-references it with a lookup table of known domain permutations generated by the "ESCU - DNSTwist Domain Names" search. This activity is significant as it can indicate phishing attempts or brand impersonation, which are common tactics used in social engineering attacks. If confirmed malicious, this could lead to unauthorized access, data theft, or reputational damage.
data_source: []
search: |-
    | tstats `security_content_summariesonly` values(All_Email.recipient) as recipients, min(_time) as firstTime, max(_time) as lastTime FROM datamodel=Email
      BY All_Email.src_user, All_Email.message_id
    | `drop_dm_object_name("All_Email")`
    | `security_content_ctime(firstTime)`
    | `security_content_ctime(lastTime)`
    | eval temp=split(src_user, "@")
    | eval email_domain=mvindex(temp, 1)
    | lookup update=true brandMonitoring_lookup domain as email_domain OUTPUT domain_abuse
    | search domain_abuse=true
    | table message_id, src_user, email_domain, recipients, firstTime, lastTime
    | `monitor_email_for_brand_abuse_filter`
how_to_implement: You need to ingest email header data. Specifically the sender's address (src_user) must be populated.  You also need to have run the search "ESCU - DNSTwist Domain Names", which creates the permutations of the domain that will be checked for.
known_false_positives: No false positives have been identified at this time.
references: []
finding:
    title: Possible Brand Abuse from $email_domain$
    entity:
        field: src_user
        type: user
        score: 50
analytic_story:
    - Brand Monitoring
    - Suspicious Emails
    - Scattered Lapsus$ Hunters
asset_type: Endpoint
mitre_attack_id: []
product:
    - Splunk Enterprise
    - Splunk Enterprise Security
    - Splunk Cloud
category: application
security_domain: network
baselines:
    - DNSTwist Domain Names

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Executable code, not a declarative rule

This submission is arbitrary [[ currentRule.format ? currentRule.format.toUpperCase() : '' ]] code, not a declarative detection rule — review it as you would any script before running it, and note that it cannot be safely aggregated or auto-executed alongside YARA/Sigma/Suricata/CRS rules.

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