Email Header Analysis Strengthening Cybersecurity Against Phishing Attacks

Phishing emails continue to pose a significant threat to organisations, serving as one of the primary attack vectors. The Mitre ATT&CK framework categorises phishing under both Initial Access and reconnaissance techniques, highlighting its prevalence in breaching organisations. In this article, we will delve into the importance of email header analysis in combating these phishing attacks and enhancing cybersecurity measures.

The Persistence of Phishing Attacks

Phishing attacks remain one of the most prevalent methods employed by attackers to breach organisations. Despite various security measures in place, such as robust email gateways and spam filters, attackers continuously adapt and enhance their phishing campaigns. In fact, the concept of Phishing-as-a-Service (PaaS) has emerged, enabling hackers to establish sophisticated phishing campaigns for a fee. This has introduced increasingly sophisticated phishing techniques to a wider audience of hackers, making it imperative for organisations to strengthen their defences.

Email Analysis within a SOC: The Importance of Suspicious Email Reporting

Emails typically enter an organisation through the email gateway, also known as the Mail Transfer Agent (MTA). While most email gateways possess robust capabilities to block spam and some phishing emails, it is crucial to encourage end-users to report any suspicious emails they encounter. Establishing a portal or an easy method for users to report such emails as suspicious allows for deeper automated analysis and/or forwarding to the SOC for awareness and in-depth analysis.

The Process of Email Analysis

The analysis of suspicious emails involves several steps to ensure a comprehensive examination:

1. Examination of Email Message Headers: Email headers contain metadata related to the email, including sender, receiver, route, and timestamp information. While some individuals may be able to interpret email headers from experience, it is common practice to use email header analysers for a more thorough examination. One widely used and freely available email header analyzer is “mxtoolbox”, which serves as a valuable tool for cybersecurity professionals.
2. Examination of Email Content: Analysing the content of the email involves scrutinising URL links, attachments (e.g., Excel, PDF), and other relevant factors. This step aims to identify any malicious elements within the email that could pose a threat to the organisation’s security.
3. Other Factors: In addition to email header and content analysis, it is essential to consider other aspects, such as the sending domain’s history and email traffic patterns. These factors can provide valuable insights into the nature of the email and help identify potential threats.

Manual vs. Automated Email Analysis

While manual email analysis methods can be time-consuming, automating the process can significantly enhance efficiency. Robust email gateways should possess the capability to automatically conduct certain analyses to determine an email’s verdict, such as identifying spam or phishing emails. This automation allows SOC analysts to focus on more complex tasks, while still benefiting from the insights provided by automated analysis.

Understanding Email Headers: Key Information for Analysis

Email headers play a crucial role in email analysis, as they contain vital metadata that helps identify the origin and path of an email. Key email header fields include:

1. Sender: The email address of the sender.
2. Receiver: The email address of the recipient.
3. Route: The sequence of email server hops that processed the email.
4. Timestamp: The date and time when the email was sent.

To view email headers, most email clients offer an option to “View Sources” or “View Headers.” This will display the entire email, including the email headers. While initially appearing as a jumble of characters, email headers contain essential details for analysis.

Email Header Analysis Tools: Simplifying the Process

Interpreting email headers can be challenging for many individuals. To simplify the analysis process, email header analysers are widely used. One popular and freely available email header analyzer is “mxtoolbox”, which provides valuable insights into the sequence of email server hops that processed the email.

Strengthening Security Measures with SPF, DKIM, and DMARC

To combat the increasing sophistication of phishing attacks, organisations have implemented additional security measures, such as SPF, DKIM, and DMARC.

1. SPF (Sender Policy Framework): SPF allows senders to include a special TXT record in DNS that outlines the authorised IP addresses responsible for sending emails on behalf of their domain. This helps verify the authenticity of the sending IP address and prevents email impersonation.
2. DKIM (DomainKeys Identified Mail): DKIM utilises Public/Private Key cryptography to validate whether the sending server is authorised to send emails. It ensures that the message remains unaltered in transit and reduces the likelihood of spammers using forged or stolen email addresses.
3. DMARC (Domain-based Message Authentication, Reporting, and Conformance): DMARC instructs receivers of emails from a domain, legitimate or spoofed, on what to do if SPF and/or DKIM checks fail. It adds an additional layer of protection against phishing attempts.

The Importance of Automated Email Analysis

Automated email analysis is crucial in today’s cybersecurity landscape. With attackers constantly evolving their tactics, relying solely on manual analysis can be time-consuming and inefficient. Automating email analysis allows SOC analysts to process a larger volume of emails and focus on more complex tasks, enhancing overall cybersecurity measures.

The Significance of Thorough Email Body and Attachment Analysis

Hackers often compromise the credentials of legitimate users and reputable companies, making it crucial to conduct thorough email body and attachment analysis. This step helps identify any malicious elements within the email and prevents successful phishing attempts. Additionally, comprehensive user training plays a vital role in educating employees about the risks associated with phishing emails and enhancing their ability to identify suspicious emails.

Mitigating Risks from Legitimate Hacked Accounts

Hackers frequently configure email auto-forwarding rules on compromised email accounts to gain control over communication flow. This manipulation allows them to send phishing emails without the legitimate owner of the email account realising that their account has been compromised. By conducting thorough email analysis, organisations can detect and mitigate the risks associated with these compromised accounts.

Conclusion

In the face of persistent phishing attacks, organisations must prioritise email header analysis as a crucial component of their cybersecurity measures. By automating email analysis processes, leveraging SPF, DKIM, and DMARC, and conducting comprehensive email body and attachment analysis, organisations can enhance their security posture and mitigate the risks posed by phishing attacks. Thorough user training further strengthens defences, making employees the first line of defence against phishing attempts. With a comprehensive approach to email header analysis, organisations can protect themselves from the ever-evolving threat landscape and safeguard their sensitive information.