Investigating a Sophisticated B2B Business Email Compromise Attack

In a recent report by Trend Micro’s Managed XDR team, a complex Business Email Compromise (BEC) attack targeting multiple organizations has been uncovered. The attackers exploited a compromised email server, allowing them to manipulate ongoing email conversations and carry out a fraudulent scheme that lasted for several days. This incident highlights the growing sophistication of cyberattacks targeting trusted business relationships.

A Detailed Analysis of the Attack

A group of skilled threat actors orchestrated a Business Email Compromise (BEC) attack that targeted a network of multiple organizations. The attackers exploited the implicit trust between three business partners to manipulate email communications and redirect funds into their control. The scheme was executed in two distinct phases.

Phase 1: Strategic Infiltration

The attackers gained access to various email accounts and an insecure third-party email server, which allowed them to send fraudulent emails without being flagged by standard security measures like SPF authentication. They carefully positioned themselves within existing email chains, waiting for approximately 4.5 hours before introducing fraudulent banking information, directing one of the partners to send funds to an attacker-controlled account.

Phase 2: Full Control and Manipulation

The second phase of the attack saw the attackers fully taking control of the conversation. They replaced legitimate email recipients with their own compromised accounts, mimicking the writing style and tone of the original parties to maintain the appearance of legitimacy. This manipulation ultimately led to a successful funds transfer into the fraudsters’ bank account.

Trend

What Undercode Say:

This particular BEC attack demonstrates a high level of sophistication and an in-depth understanding of how business communications work. The attackers didn’t simply hijack an email account—they infiltrated email conversations at the right moment, gaining the trust of the partners involved and manipulating them into transferring funds. By exploiting an insecure third-party email server, the attackers bypassed common authentication protocols, making it much harder to detect the fraudulent messages.

The ability to control an ongoing conversation and mimic the tone of the original participants highlights the need for businesses to implement better authentication protocols, especially with high-value transactions like financial transfers. The use of a compromised third-party email server is especially concerning, as it reveals the vulnerabilities that may exist in business partnerships, where third-party infrastructure isn’t always properly secured.

BEC attacks are becoming increasingly common, and the methods employed by attackers are growing more sophisticated. The case is an example of how cybercriminals can manipulate the trust between organizations and exploit weaknesses in email security to achieve their objectives. This type of attack is particularly dangerous because it preys on the implicit trust that exists in everyday business communication, where no one expects a partner to be compromised.

Businesses must consider several strategies to protect themselves from such attacks. Strengthening email security with DMARC, DKIM, and SPF is critical to ensure that fraudulent emails are blocked. Digital signatures should be used for any financial transactions, and organizations should implement strict auditing for high-profile employees to monitor any suspicious activities. Additionally, companies should establish clear protocols for verifying financial transactions with out-of-band communication to prevent unauthorized transfers.

Lastly, educating employees and fostering a culture of cybersecurity awareness is essential. Even with strong technical defenses, human errors and lack of awareness often remain a key vulnerability. By addressing both technical and human factors, companies can better protect themselves from these increasingly sophisticated BEC attacks.

Fact Checker Results

The details of the attack were corroborated by Trend Micro’s analysis, revealing the use of MITRE ATT&CK techniques such as email collection, account takeover, and exploiting third-party infrastructure.
The recommendation for stronger email security protocols (DMARC, DKIM, SPF) and digital signatures aligns with industry best practices to counter BEC attacks.
The attack’s sophistication, especially the timing of interventions and the manipulation of conversations, underlines the evolving nature of cyber threats targeting businesses.

References:

Reported By: https://cyberpress.org/hackers-abuse-breached-email-servers/
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