Monitor Email for Brand Abuse via Domain Permutations

This detection focuses on identifying potential brand abuse by monitoring email communications. The analytic leverages email header data, specifically the sender’s address (src_user), and compares it against a lookup table of known domain permutations. These permutations are generated by the “ESCU - DNSTwist Domain Names” search. This technique is significant because attackers often use slightly altered domain names to impersonate legitimate organizations in phishing campaigns. By identifying these lookalike domains, organizations can proactively detect and mitigate potential brand abuse and social engineering attacks. If attackers are successful, this can lead to unauthorized access, data theft, and reputational damage. The detection logic is implemented within Splunk and requires the Email data model to be populated. The brandMonitoring_lookup table must be configured with monitored domains for effective detection.

Attack Chain

1. The attacker registers a domain name that is a permutation of the legitimate brand’s domain (e.g., using DNSTwist or similar tools).
2. The attacker crafts a phishing email that appears to originate from the spoofed domain.
3. The attacker sends the phishing email to potential victims, often targeting employees or customers of the legitimate brand.
4. The recipient opens the email and may be prompted to click on a link or download an attachment.
5. If the recipient clicks on a link, they may be redirected to a malicious website designed to steal credentials or install malware.
6. If the recipient downloads an attachment, it may contain malware that infects their system.
7. The attacker gains unauthorized access to the victim’s system or network.
8. The attacker may then steal sensitive data, install ransomware, or perform other malicious activities.

Impact

Successful brand abuse can lead to significant financial and reputational damage. Customers may lose trust in the brand, and the organization may incur costs associated with incident response, data breach notification, and legal fees. The impact depends on the scale of the phishing campaign and the sensitivity of the data compromised. This can affect any organization, but is especially harmful to those in regulated industries or those that rely heavily on customer trust.

Recommendation

• Ensure that email header data is ingested and the All_Email.src_user field is populated as described in the “how_to_implement” section.
• Implement and regularly update the “ESCU - DNSTwist Domain Names” search to generate domain permutations for the brandMonitoring_lookup table.
• Deploy the provided analytic in Splunk Enterprise Security to identify potential brand abuse attempts.
• Investigate and respond to any alerts generated by the analytic, prioritizing those with high confidence scores.
• Tune the monitor_email_for_brand_abuse_filter macro to reduce false positives based on your specific environment and known email traffic patterns.
• Enable Sysmon process creation logging to enhance visibility into potential malware execution following a successful phishing attack.