23 August 2026 · DMARC Engine · 34 min read
The Insider Threat: Compromised Internal Accounts
Compromised internal accounts pose a significant threat to organisations, as they can be used to send malicious emails that appear to originate from a trusted source. This can lead to a loss of customer trust, damage to the organisation's reputation, and financial losses. In our experience, compromised internal accounts are often used to send phishing emails, distribute malware, or conduct business email compromise (BEC) attacks.
To illustrate this, consider a company like Example Ltd, which has a DMARC record set to p=none to monitor email traffic. If an attacker compromises an internal account, they can use it to send emails that appear to come from Example Ltd. These emails may not be caught by traditional security controls, as they are sent from a legitimate email account.
In a hosted or managed DMARC setup, such as the one we operate at DMARC Engine, we can help organisations identify and mitigate these threats by monitoring their DMARC reports for suspicious activity. For instance, if we notice a sudden spike in emails sent from an internal account to external recipients, we can flag this activity as potentially malicious.
One of the key challenges in detecting compromised internal accounts is that the emails sent from these accounts often appear to be legitimate. They may use the correct domain name, and the sender's email address may be spoofed to look like it comes from a real employee. To overcome this, we use a combination of DMARC data and other security controls, such as email authentication protocols like SPF and DKIM.
For example, if an email is sent from an internal account, but it fails SPF or DKIM validation, this could indicate that the email is malicious. We can use this information to flag the email for further review, or to block it altogether.
Here is an example of what a DMARC report might look like for an email that fails SPF validation:
<record>
<row>
<source_ip>192.0.2.1</source_ip>
<count>10</count>
<policy_evaluated>
<disposition>none</disposition>
<dkim>fail</dkim>
<spf>fail</spf>
</policy_evaluated>
</row>
</record>In this example, the email was sent from the IP address 192.0.2.1, and it failed both SPF and DKIM validation. This suggests that the email may be malicious, and we can use this information to take further action.
Another challenge in detecting compromised internal accounts is that attackers often use tactics like email impersonation to make their emails appear more legitimate. For instance, an attacker may send an email that appears to come from a real employee, but with a slightly different email address. To detect this type of activity, we use advanced analytics and machine learning algorithms to identify patterns in email traffic that may indicate malicious activity.
In a managed DMARC setup, we can also help organisations to optimise their DMARC configuration to improve threat detection. For example, we can help organisations to set up a DMARC record with a p=reject policy, which will reject emails that fail DMARC validation. We can also help organisations to configure their email servers to use email authentication protocols like SPF and DKIM, which can help to prevent email spoofing.
To illustrate this, consider a company like Example Ltd, which has a DMARC record set to p=none. To improve threat detection, we might recommend that they update their DMARC record to p=reject, like this:
_dmarc.example.com. IN TXT "v=DMARC1; p=reject; pct=100; rua=mailto:dmarc@example.com"This will reject emails that fail DMARC validation, which can help to prevent malicious emails from being delivered to recipients.
In addition to configuring DMARC, we also recommend that organisations implement other security controls, such as multi-factor authentication (MFA) and regular password rotation. These controls can help to prevent internal accounts from being compromised in the first place, which can reduce the risk of malicious emails being sent.
In our experience, compromised internal accounts are a significant threat to organisations, and DMARC can be a powerful tool in detecting and mitigating these threats. By monitoring DMARC reports, using advanced analytics and machine learning algorithms, and optimising DMARC configuration, organisations can improve their threat detection capabilities and prevent malicious emails from being delivered to recipients.
We also recommend that organisations regularly review their DMARC reports to identify suspicious activity, and take prompt action to investigate and remediate any potential security incidents. By taking a proactive approach to email security, organisations can help to protect their customers, employees, and reputation from the threats posed by compromised internal accounts.
In terms of specific recommendations, we suggest that organisations follow these best practices:
* Monitor DMARC reports regularly to identify suspicious activity
* Use advanced analytics and machine learning algorithms to identify patterns in email traffic that may indicate malicious activity
* Optimise DMARC configuration to improve threat detection, such as setting up a DMARC record with a p=reject policy
* Implement other security controls, such as MFA and regular password rotation, to prevent internal accounts from being compromised
* Regularly review and update email authentication protocols, such as SPF and DKIM, to prevent email spoofing.
By following these best practices, organisations can help to protect themselves from the threats posed by compromised internal accounts, and improve their overall email security posture.
DMARC Reporting: A Window into Internal Account Abuse
DMARC reporting is a crucial component in identifying and mitigating email threats from compromised internal accounts. The aggregate reports, also known as RUA reports, provide a wealth of information on email authentication results, which can be used to pinpoint potential security issues. In a hosted or managed setup, such as the one we operate at DMARC Engine, these reports are collected and analysed daily to identify suspicious patterns and anomalies.
One of the key benefits of DMARC reporting is that it provides a colour-coded view of an organisation's email authentication posture. By analysing the reports, security teams can quickly identify which emails are being sent from compromised internal accounts, and take corrective action to prevent further abuse. For instance, a report may show a high volume of emails being sent from a specific IP address, with a low DMARC alignment rate, indicating potential spam or phishing activity.
To illustrate this, let's consider an example of a DMARC report snippet:
<record>
<row>
<source_ip>192.0.2.1</source_ip>
<count>100</count>
<policy_evaluated>
<disposition>none</disposition>
<dkim>fail</dkim>
<spf>fail</spf>
</policy_evaluated>
</row>
</record>In this example, the report shows that 100 emails were sent from the IP address 192.0.2.1, with both DKIM and SPF failing to authenticate. This could indicate that the emails were sent from a compromised internal account, and the organisation's security team should investigate further.
In a managed setup, we would typically organise these reports by domain, IP address, and authentication result, to make it easier to identify patterns and anomalies. We would also use automated tools to analyse the reports and generate alerts for potential security issues. For instance, we may set up a rule to alert the security team if a report shows a high volume of emails being sent from a specific IP address, with a low DMARC alignment rate.
Another important aspect of DMARC reporting is the ability to identify and mitigate email threats in real-time. By analysing the reports in real-time, security teams can quickly respond to potential security issues, and prevent further abuse. This is particularly important in the case of compromised internal accounts, where every minute counts in preventing further damage.
To optimise DMARC reporting for threat detection, we recommend the following best practices:
- Collect and analyse DMARC reports daily, to identify suspicious patterns and anomalies.
- Organise reports by domain, IP address, and authentication result, to make it easier to identify patterns and anomalies.
- Use automated tools to analyse reports and generate alerts for potential security issues.
- Set up rules to alert the security team if a report shows a high volume of emails being sent from a specific IP address, with a low DMARC alignment rate.
- Use a managed setup, such as the one we operate at DMARC Engine, to simplify the process of collecting and analysing DMARC reports.
By following these best practices, organisations can use DMARC reporting to identify and mitigate email threats from compromised internal accounts, and improve their overall email security posture. In the next section, we will delve deeper into aggregate report analysis, and explore how to identify suspicious patterns and anomalies in DMARC reports.
Aggregate Report Analysis: Identifying Suspicious Patterns
When analysing aggregate reports, the centre of attention should be on identifying suspicious patterns that may indicate email threats from compromised internal accounts. A key challenge is to distinguish between legitimate and malicious email activity, as the colour of the report data can be misleading. For instance, a high volume of emails from a specific IP address may seem suspicious at first glance, but it could be a legitimate mailing list or a marketing campaign.
To optimise the analysis process, it is essential to consider the organisational context and the typical email traffic patterns. Our team at DMARC Engine has found that understanding the customer's email ecosystem is crucial in identifying potential threats. We organise the report data by domain, IP address, and email authentication results to pinpoint anomalies.
One common pattern we see is a sudden spike in email volume from a specific IP address or domain, which may indicate a compromised account. For example,
{
"org_name": "example.com",
"date_range": {
"start": "2022-01-01",
"end": "2022-01-07"
},
"records": [
{
"row": {
"source_ip": "192.0.2.1",
"count": 1000,
"policy_evaluated": {
"disposition": "none",
"dkim": "fail",
"spf": "fail"
}
}
},
{
"row": {
"source_ip": "198.51.100.1",
"count": 500,
"policy_evaluated": {
"disposition": "none",
"dkim": "fail",
"spf": "fail"
}
}
}
]
}In this example, the IP address 192.0.2.1 has sent 1000 emails, while 198.51.100.1 has sent 500 emails, both with failed DKIM and SPF authentication. This could be a sign of a compromised internal account, especially if the email volume is unusually high compared to the typical traffic pattern.
Another pattern to watch out for is emails with failed authentication results, such as failed DKIM or SPF. While occasional failures can be expected due to misconfiguration or transient issues, a consistent pattern of failures may indicate a malicious actor attempting to send emails from a compromised account. Our team has seen cases where an attacker has attempted to send phishing emails with spoofed sender addresses, which can be detected by monitoring the authentication results.
In a hosted or managed setup, such as the one provided by DMARC Engine, the analysis process can be streamlined by leveraging automated tools and expert knowledge. Our platform provides real-time reporting and analysis, enabling customers to quickly identify and respond to potential threats. We also offer customised reporting and alerting, which can be tailored to the customer's specific needs and threat landscape.
When analysing aggregate reports, it is also essential to consider the trade-offs between security and deliverability. Overly restrictive policies can lead to false positives, where legitimate emails are blocked or flagged as spam. On the other hand, overly permissive policies can allow malicious emails to slip through. Our team works closely with customers to strike the right balance between security and deliverability, ensuring that their email ecosystem is protected without disrupting legitimate email activity.
In addition to identifying suspicious patterns, aggregate report analysis can also provide valuable insights into the organisational email ecosystem. By monitoring email traffic patterns and authentication results, customers can identify areas for improvement, such as optimising their SPF records or implementing DKIM signing. Our team provides guidance and recommendations on how to improve email authentication and security, helping customers to optimise their email infrastructure and prevent email threats.
In short, aggregate report analysis is a critical component of identifying and mitigating email threats from compromised internal accounts. By considering the organisational context, monitoring email traffic patterns, and analysing authentication results, customers can quickly identify potential threats and take corrective action. With the right tools and expertise, such as those provided by DMARC Engine, customers can protect their email ecosystem and prevent email threats.
Dissecting a Real-World Example: DMARC Report Snippets
When analysing DMARC reports, it is crucial to understand the various components that make up these reports, and how to interpret the data to identify potential email threats from compromised internal accounts. In our experience, a hosted DMARC setup can simplify the process of collecting and analysing these reports, but it is still essential to have a deep understanding of the report snippets to make informed decisions.
Let's consider a real-world example of a DMARC report snippet, which can help illustrate the process of identifying and mitigating email threats. The following report snippet is from a company that has implemented DMARC with a policy of p=none, which means they are monitoring email authentication results but not blocking emails that fail authentication:
<feedback>
<report_metadata>
<org_name>example.com</org_name>
<email>abuse@example.com</email>
<extra_contact_info>https://example.com/dmarc</extra_contact_info>
<report_id>1234567890</report_id>
<date_range>
<begin>1643723400</begin>
<end>1646315200</end>
</date_range>
</report_metadata>
<policy_published>
<domain>example.com</domain>
<adkim>r</adkim>
<aspf>r</aspf>
<p>none</p>
<sp>none</sp>
<pct>100</pct>
</policy_published>
<record>
<row>
<source_ip>192.0.2.1</source_ip>
<count>10</count>
<policy_evaluated>
<disposition>none</disposition>
<dkim>pass</dkim>
<spf>fail</spf>
</policy_evaluated>
</row>
<identifiers>
<header_from>example.com</header_from>
</identifiers>
<auth_results>
<dkim>
<domain>example.com</domain>
<result>pass</result>
<selector>selector1</selector>
</dkim>
<spf>
<domain>example.com</domain>
<result>fail</result>
<scope>mfrom</scope>
</spf>
</auth_results>
</record>
</feedback>In this example, the report snippet shows that there were 10 emails sent from the IP address 192.0.2.1 with a From header domain of example.com. The emails passed DKIM authentication but failed SPF authentication. This could indicate a potential issue with the company's SPF configuration, or it could be a sign of a compromised internal account being used to send emails.
To investigate further, we would need to analyse the email headers and content to determine the intent and origin of the emails. In a hosted DMARC setup, this process can be automated to some extent, with the system alerting administrators to potential issues and providing tools to analyse the email data.
Another important aspect to consider when analysing DMARC reports is the concept of "domain alignment". Domain alignment refers to the process of verifying that the domain in the From header of an email matches the domain in the DKIM or SPF authentication results. In the example above, the domain in the From header is example.com, which matches the domain in the DKIM authentication result. However, the SPF authentication result shows a failure, which could indicate a domain alignment issue.
In our experience, domain alignment issues can be a common cause of false positives in DMARC reports. To mitigate this, it is essential to ensure that the SPF and DKIM configurations are correct and up-to-date, and that the domains in the From header and authentication results are aligned. A hosted DMARC setup can help simplify this process by providing tools to automate domain alignment checks and alert administrators to potential issues.
When analysing DMARC reports, it is also crucial to consider the concept of "selector rotation". Selector rotation refers to the process of rotating the selectors used in DKIM authentication to prevent attackers from exploiting a single selector. In the example above, the DKIM selector is selector1, which may be a static selector that is used for all emails. To improve security, it is recommended to rotate the selectors regularly, using a combination of automated tools and manual processes.
In a hosted DMARC setup, selector rotation can be automated to some extent, with the system generating new selectors and updating the DKIM configuration accordingly. However, it is still essential to monitor the DMARC reports and adjust the selector rotation strategy as needed to ensure optimal security and deliverability.
Finally, when analysing DMARC reports, it is essential to consider the trade-offs between security and deliverability. A strict DMARC policy can help prevent email threats, but it can also block legitimate emails if the configuration is not correct. In our experience, a balanced approach is often the best strategy, with a combination of monitoring and blocking used to achieve optimal security and deliverability.
For example, a company may choose to implement a DMARC policy of p=quarantine, which would quarantine emails that fail authentication rather than blocking them outright. This can help prevent email threats while also ensuring that legitimate emails are not blocked. A hosted DMARC setup can help simplify this process by providing tools to automate the quarantine process and alert administrators to potential issues.
In conclusion to this section, analysing DMARC reports requires a deep understanding of the various components that make up these reports, as well as the trade-offs between security and deliverability. By considering the concepts of domain alignment, selector rotation, and balanced policies, administrators can use DMARC reports to identify and mitigate email threats from compromised internal accounts, while also ensuring optimal deliverability. In the next section, we will discuss how to use DMARC data to inform incident response.
Using DMARC Data to Inform Incident Response
When a security incident occurs, every minute counts, and the centre of attention is on containing the breach and mitigating its impact. DMARC data can be a crucial component in informing incident response, particularly when dealing with compromised internal accounts. The key to effective incident response lies in swift analysis and action, and DMARC reports can provide vital insights into the nature and extent of the compromise.
In our experience managing DMARC for numerous customers, we've seen firsthand how DMARC data can guide the incident response process. For instance, when a customer's internal account is compromised, and spam emails are sent from their domain, DMARC reports will often show a spike in authentication failures from unfamiliar sources. This information can be used to pinpoint the source of the compromise and take corrective action.
One of the primary challenges in using DMARC data for incident response is filtering out the noise. DMARC reports can be verbose, with a large volume of data that may not be directly relevant to the incident at hand. To optimise the process, it's essential to have a system in place for parsing and analysing DMARC reports in real-time. This can involve setting up automated scripts to extract key information, such as sender IP addresses and message headers, and using this data to inform the incident response strategy.
A hosted or managed DMARC setup can significantly simplify this process by providing pre-built tools and expertise for analysing DMARC reports. For example, our team at DMARC Engine uses custom-built software to parse DMARC reports and identify suspicious patterns, which enables us to provide our customers with actionable intelligence on potential security threats.
{
"org_name": "example.com",
"date_range": {
"start": "2022-01-01",
"end": "2022-01-31"
},
"records": [
{
"source_ip": "192.0.2.1",
"count": 100,
"disposition": "none",
"dkim": "fail",
"spf": "fail"
},
{
"source_ip": "198.51.100.1",
"count": 50,
"disposition": "quarantine",
"dkim": "pass",
"spf": "fail"
}
]
}The snippet above shows an example of a DMARC aggregate report, which includes information on the source IP address, message count, disposition, and authentication results. By analysing this data, security teams can identify potential security threats and take corrective action to mitigate them. For instance, if the report shows a large number of messages from an unfamiliar source IP address with a high failure rate for DKIM and SPF, this could indicate a compromised internal account.
Another critical aspect of using DMARC data for incident response is understanding the trade-offs between security and deliverability. Implementing a strict DMARC policy can help prevent spam and phishing attacks, but it may also block legitimate emails. Therefore, it's essential to strike a balance between security and deliverability, particularly during the incident response process.
In our experience, a DMARC policy with a disposition of quarantine can be an effective way to balance security and deliverability. This approach allows security teams to isolate potentially malicious emails without blocking them entirely, which can help prevent false positives and ensure that legitimate emails are delivered. However, this approach requires careful monitoring and analysis of DMARC reports to ensure that the quarantine policy is effective in preventing security threats.
To optimise DMARC for incident response, security teams should also consider implementing a robust monitoring and alerting system. This can involve setting up custom alerts for suspicious DMARC report data, such as a sudden spike in authentication failures or a large number of messages from an unfamiliar source IP address. By providing real-time alerts and insights, security teams can respond quickly to potential security threats and mitigate their impact.
In addition to monitoring and alerting, security teams should also consider implementing a process for regular DMARC report analysis and review. This can involve scheduling regular reviews of DMARC reports to identify suspicious patterns and potential security threats. By taking a proactive approach to DMARC report analysis, security teams can stay ahead of potential security threats and ensure that their organisation's email ecosystem remains secure.
In short, DMARC data can be a powerful tool in informing incident response, particularly when dealing with compromised internal accounts. By leveraging DMARC reports and implementing a robust monitoring and alerting system, security teams can respond quickly to potential security threats and mitigate their impact. However, this requires careful consideration of the trade-offs between security and deliverability, as well as a deep understanding of DMARC report data and its limitations. With the right approach and tools in place, DMARC can be a crucial component in an organisation's incident response strategy, helping to protect against email-based security threats and ensure the integrity of the email ecosystem.
Operational Guidance: Configuring DMARC for Threat Detection
Configuring DMARC for threat detection requires careful consideration of several factors, including the organisation's email infrastructure, security posture, and incident response processes. A well-configured DMARC setup can provide valuable insights into email threats originating from compromised internal accounts, but it also requires ongoing monitoring and analysis to optimise its effectiveness.
When setting up DMARC, it is essential to start with a monitoring-only configuration, using the none policy in the DMARC record. This allows the organisation to collect data on email traffic without affecting email delivery. The DMARC record should be published in the organisation's DNS, and it is crucial to ensure that the record is correctly formatted and includes all the necessary tags. For example:
_dmarc.example.com. IN TXT "v=DMARC1; p=none; pct=100; rua=mailto:dmarc@example.com; ruf=mailto:dmarc@example.com; fo=1"In this example, the DMARC record specifies a monitoring-only policy (p=none), with 100% of email traffic being monitored (pct=100). The rua tag specifies the email address where aggregate reports will be sent, while the ruf tag specifies the email address where failure reports will be sent. The fo tag is used to specify the format of the failure reports.
Once the DMARC record is in place, it is essential to monitor the aggregate reports to identify potential email threats. These reports provide a wealth of information on email traffic, including the number of emails sent, the number of emails that passed or failed DMARC validation, and the IP addresses of the sending servers. By analysing these reports, organisations can identify suspicious patterns and trends that may indicate compromised internal accounts.
In a hosted or managed setup, such as the one provided by DMARC Engine, the process of configuring DMARC for threat detection is streamlined and automated. The hosted setup provides a centralised dashboard for monitoring DMARC reports, making it easier to identify and respond to email threats. Also, the managed setup provides access to a team of experts who can help with the configuration and analysis of DMARC reports.
One of the key challenges in configuring DMARC for threat detection is determining the optimal policy setting. The none policy is typically used for monitoring-only configurations, while the quarantine policy is used to flag emails that fail DMARC validation for further review. The reject policy is the most restrictive, and it is used to block emails that fail DMARC validation. However, this policy can also lead to false positives, where legitimate emails are blocked.
To mitigate this risk, it is essential to carefully evaluate the organisation's email traffic and security posture before implementing a reject policy. This may involve analysing the aggregate reports to identify the sources of email traffic and the types of emails that are being sent. It may also involve implementing additional security controls, such as email authentication and encryption, to reduce the risk of email threats.
In addition to configuring the DMARC policy, it is also essential to configure the reporting settings to ensure that the organisation receives the necessary information to identify and respond to email threats. This includes specifying the email addresses where aggregate and failure reports will be sent, as well as the format of the reports.
The reporting settings can be configured using the rua and ruf tags in the DMARC record. For example:
_dmarc.example.com. IN TXT "v=DMARC1; p=none; pct=100; rua=mailto:dmarc@example.com; ruf=mailto:dmarc@example.com; fo=1"In this example, the rua tag specifies that aggregate reports will be sent to the dmarc@example.com email address, while the ruf tag specifies that failure reports will be sent to the same email address. The fo tag specifies that the failure reports will be sent in a format that includes the full email message.
By configuring DMARC for threat detection and monitoring the aggregate reports, organisations can gain valuable insights into email threats originating from compromised internal accounts. This information can be used to inform incident response processes and to optimise the organisation's email security posture. However, it is essential to carefully evaluate the organisation's email traffic and security posture before implementing a DMARC policy, and to continually monitor and analyse the aggregate reports to ensure the effectiveness of the DMARC setup.
In terms of specific recommendations, we suggest the following:
- Start with a monitoring-only configuration using the
nonepolicy, and gradually move to a more restrictive policy as the organisation becomes more comfortable with the DMARC setup. - Carefully evaluate the organisation's email traffic and security posture before implementing a
rejectpolicy. - Implement additional security controls, such as email authentication and encryption, to reduce the risk of email threats.
- Continually monitor and analyse the aggregate reports to identify suspicious patterns and trends.
- Use a hosted or managed setup, such as the one provided by DMARC Engine, to streamline and automate the process of configuring DMARC for threat detection.
By following these recommendations and carefully configuring DMARC for threat detection, organisations can effectively identify and mitigate email threats originating from compromised internal accounts, and optimise their email security posture to prevent future threats.
Trade-Offs and Considerations: Balancing Security and Deliverability
When implementing DMARC to identify and mitigate email threats from compromised internal accounts, organisations must balance security and deliverability considerations. A key trade-off is the level of strictness in DMARC policies, which can impact the delivery of legitimate emails. For instance, a policy of p=reject can prevent phishing attacks, but may also block emails from internal accounts that are not properly configured, such as those using third-party services that do not support DMARC.
To mitigate this risk, organisations can start with a p=none policy, which allows them to monitor DMARC reports without affecting email delivery. This approach enables them to identify potential issues and adjust their configuration before moving to a stricter policy. In a hosted or managed setup, such as the one provided by DMARC Engine, this process can be streamlined through automated reporting and analysis tools. For example, our platform provides a colour-coded dashboard that highlights potential delivery issues, allowing organisations to optimise their DMARC configuration and minimise the risk of blocking legitimate emails.
Another consideration is the impact of DMARC on email services that use internal accounts to send emails on behalf of users, such as CRM systems or marketing automation tools. These services may not be configured to support DMARC, and may therefore be blocked by a strict DMARC policy. To address this issue, organisations can use the spf and dkim alignment options to specify which email services are allowed to send emails on their behalf. For example, the following DMARC record snippet allows emails sent by a CRM system to be exempt from DMARC checks:
_dmarc.example.com. IN TXT "v=DMARC1; p=none; spf=relaxed; dkim=relaxed; aspfs=crm.example.com; adkim=crm.example.com"In this example, the aspfs and adkim options specify that emails sent by the CRM system (crm.example.com) are allowed to be exempt from DMARC checks. This approach requires careful planning and configuration to ensure that only authorised email services are exempt from DMARC checks.
Organisations must also consider the impact of DMARC on their internal email infrastructure, particularly if they have a complex email setup with multiple mail transfer agents (MTAs) and email gateways. In such cases, DMARC reports may highlight issues with email authentication and delivery that require attention from the email administrators. For instance, a DMARC report may show that emails sent from a particular MTA are not being authenticated correctly, indicating a configuration issue that needs to be addressed. In a hosted or managed setup, our team works closely with email administrators to identify and resolve these issues, ensuring that DMARC is configured to optimise both security and deliverability.
The use of subdomains is another important consideration when implementing DMARC. Organisations may use subdomains for various purposes, such as branding or geographic segmentation, and these subdomains may have their own DMARC policies. To ensure consistent security and deliverability, organisations should configure DMARC policies for each subdomain, taking into account the specific email services and infrastructure used by each subdomain. For example, a company may use a subdomain for its European operations (eu.example.com), which requires a separate DMARC policy to accommodate the different email services used in that region.
In addition to these technical considerations, organisations must also consider the operational impact of DMARC on their incident response processes. DMARC reports can provide valuable insights into potential security threats, but require careful analysis and interpretation to identify genuine threats. Our team has seen cases where DMARC reports have highlighted suspicious email activity that was not immediately apparent from other security monitoring tools. For instance, a DMARC report may show a sudden spike in emails sent from a compromised internal account, indicating a potential phishing attack that requires immediate attention.
To optimise the use of DMARC for threat detection and prevention, organisations should integrate DMARC reports into their existing incident response processes. This may involve automated alerting and notification systems, as well as regular review and analysis of DMARC reports to identify potential security threats. In a hosted or managed setup, our platform provides automated alerting and reporting tools that can be integrated with existing security information and event management (SIEM) systems, allowing organisations to respond quickly and effectively to potential security threats.
Finally, organisations must consider the ongoing maintenance and optimisation of their DMARC configuration to ensure that it remains effective in identifying and mitigating email threats from compromised internal accounts. This requires regular review and analysis of DMARC reports, as well as updates to the DMARC configuration to reflect changes in the organisation's email infrastructure and services. In a hosted or managed setup, our team works closely with organisations to ensure that their DMARC configuration is optimised for both security and deliverability, and that they receive regular updates and recommendations to improve their email security posture.
In short, implementing DMARC to identify and mitigate email threats from compromised internal accounts requires careful consideration of security and deliverability trade-offs. Organisations must balance the level of strictness in their DMARC policies with the need to ensure legitimate emails are delivered, and must consider the impact of DMARC on their internal email infrastructure and services. By taking a careful and considered approach to DMARC implementation, and by integrating DMARC reports into their incident response processes, organisations can optimise their email security posture and prevent email threats from compromised internal accounts.
Case Study: Mitigating Email Threats with DMARC at a Large Enterprise
A large enterprise, which we will refer to as CentrePoint, approached us to organise their email security infrastructure, specifically to mitigate email threats originating from compromised internal accounts. CentrePoint operates in the finance sector, making them a high-value target for phishing and business email compromise (BEC) attacks. Their existing email security setup was not optimised to detect and prevent emails sent from internal accounts that had been compromised.
To centre our efforts on the most critical aspect of their email security, we began by analysing their DMARC aggregate reports. These reports provided a colour of the email traffic landscape, highlighting potential security issues. The initial reports showed a significant number of emails failing DMARC authentication, which indicated a substantial risk of phishing and BEC attacks. We identified that a large proportion of these emails were being sent from internal accounts, but via external mail servers, a clear sign of account compromise.
Our first step was to configure DMARC to monitor all email traffic from CentrePoint's domain. We set the policy to "none" to start collecting data without affecting email delivery. This allowed us to gather intelligence on the sources of their email traffic without interrupting legitimate communications. The DMARC reports started to paint a detailed picture of CentrePoint's email ecosystem, including mail servers, third-party services, and potential security vulnerabilities.
One of the key findings from the initial DMARC reports was the presence of unauthorized mail servers sending emails on behalf of CentrePoint. These servers were not part of CentrePoint's official infrastructure, indicating that they were either compromised internal servers or external servers used by attackers. We found snippets like the following in the DMARC reports:
{
"source_ip": "192.0.2.1",
"count": 50,
"disposition": "none",
"dkim": "fail",
"spf": "fail"
}This snippet shows 50 emails sent from the IP address 192.0.2.1 with both DKIM and SPF failing, a strong indicator of unauthorized email activity.
To mitigate these threats, we worked with CentrePoint to implement a more restrictive DMARC policy, gradually moving from "none" to "quarantine" and eventually to "reject" for emails failing authentication. This approach ensured that emails from compromised accounts or unauthorized servers were blocked from reaching recipients, thus preventing potential phishing and BEC attacks.
However, implementing a strict DMARC policy comes with trade-offs, particularly concerning deliverability. CentrePoint, like many organisations, relies on a variety of third-party services that send emails on their behalf. These services might not be fully aligned with DMARC best practices, potentially leading to false positives and blocked legitimate emails. To optimise for both security and deliverability, we had to carefully manage the DMARC policy exceptions and ensure that all legitimate email sources were properly configured for DMARC authentication.
In a hosted or managed DMARC setup, handling these exceptions and configurations can be more straightforward, as the provider often has tools and expertise to manage complex email ecosystems. For instance, our platform at DMARC Engine provides features to easily manage and monitor DMARC policies, including automated exception handling and detailed reporting to help identify and mitigate potential issues.
Another critical aspect of our work with CentrePoint was educating their IT and security teams about the importance of monitoring DMARC reports and how to use the insights gained to inform incident response. By regularly analysing DMARC aggregate reports, CentrePoint can now identify patterns of suspicious email activity indicative of internal account compromise. For example, a sudden spike in emails failing DMARC authentication from a specific IP address or mail server can signal a potential security incident.
To further enhance their email security posture, we recommended that CentrePoint implement additional security measures, such as multi-factor authentication (MFA) for all email accounts and regular security awareness training for employees to prevent phishing attacks. These measures, combined with a well-configured DMARC setup, significantly reduce the risk of email threats from compromised internal accounts.
In conclusion to this case study, CentrePoint's experience highlights the importance of DMARC in identifying and mitigating email threats from compromised internal accounts. By carefully configuring DMARC policies, monitoring aggregate reports, and taking a proactive approach to email security, organisations can significantly enhance their defences against phishing and BEC attacks. As part of an overall email security strategy, DMARC is a powerful tool that provides visibility into email traffic and helps prevent attacks, making it an essential component for any organisation looking to optimise its email security infrastructure.
Optimising DMARC for Ongoing Threat Detection and Prevention
To truly leverage DMARC for identifying and mitigating email threats from compromised internal accounts, it is crucial to optimise its configuration and ongoing management. This involves a deep understanding of the trade-offs between security and deliverability, as well as the nuances of DMARC reporting and analysis. In our experience at DMARC Engine, where we host and manage DMARC, SPF, DKIM, MTA-STS, and BIMI for customers, the key to effective DMARC optimisation lies in meticulous monitoring and swift action based on insights gleaned from aggregate reports.
One of the primary challenges in optimising DMARC is navigating the balance between blocking malicious emails and ensuring legitimate emails are delivered. A strict DMARC policy can prevent phishing attacks but may also block emails from legitimate sources that are not properly configured. For instance, a company might use a third-party service for sending newsletters, which could be blocked if the service does not align with the company's DMARC policy. To mitigate this, it's essential to implement a monitoring system that can quickly identify and address false positives, ensuring that legitimate emails are not unduly blocked.
Monitoring and Analysis
Effective monitoring of DMARC aggregate reports (RUA) is at the centre of optimising DMARC for threat detection. These reports provide a colour of the email sending landscape, highlighting potential issues with SPF, DKIM, and DMARC alignment. For example, a sudden spike in emails failing DMARC validation from a specific IP address could indicate a compromised internal account.
Example of an aggregate report snippet:
<record>
<row>
<source_ip>192.0.2.1</source_ip>
<count>100</count>
<policy_evaluated>
<disposition>none</disposition>
<dkim>fail</dkim>
<spf>fail</spf>
</policy_evaluated>
</row>
</record>In a hosted or managed setup like DMARC Engine, these reports are automatically collected and analysed, providing customers with actionable insights without the need for extensive in-house expertise.
Policy Management
Managing DMARC policies effectively is critical for optimising threat detection and prevention. This involves gradually tightening the DMARC policy from none to quarantine and eventually to reject as the organisation becomes more confident in its email ecosystem's integrity. However, this process must be carefully managed to avoid disrupting legitimate email flows. For example, moving from none to quarantine might require setting up additional mailboxes to handle the quarantined emails, ensuring they are reviewed and released if legitimate.
SPF and DKIM Alignment
Ensuring SPF and DKIM are properly aligned and configured is fundamental to effective DMARC optimisation. Misconfigured SPF records can lead to false positives, where legitimate emails are blocked, while DKIM misconfiguration can result in emails failing DMARC validation. Regular audits of SPF and DKIM configurations are necessary to optimise DMARC performance. In our experience, using a managed service can simplify this process by providing tools and expertise to maintain accurate and up-to-date configurations.
Organisational Considerations
Beyond the technical aspects, organisational considerations play a significant role in DMARC optimisation. Incident response plans must be in place to quickly respond to threats identified through DMARC analysis. This includes procedures for isolating compromised accounts, notifying affected parties, and taking corrective actions to prevent future incidents. Also, ongoing employee education is crucial, as phishing attacks often target internal accounts, and vigilant employees can be the first line of defence against such threats.
Automation and Integration
To truly optimise DMARC for ongoing threat detection and prevention, automation and integration with existing security tools are essential. Automated systems can monitor DMARC reports, identify potential threats, and trigger incident response processes more efficiently than manual monitoring. Integration with SIEM (Security Information and Event Management) systems, for example, can provide a comprehensive view of email security threats alongside other security events, enabling more effective threat hunting and response.
In conclusion to this section, optimising DMARC for identifying and mitigating email threats from compromised internal accounts requires a multifaceted approach. It involves meticulous monitoring of DMARC reports, careful management of DMARC policies, ensuring SPF and DKIM alignment, organisational preparedness, and the strategic use of automation and integration. By focusing on these areas and leveraging the insights gained from DMARC analysis, organisations can significantly enhance their email security posture and protect against the evolving threats posed by compromised internal accounts.