In a significant cybersecurity incident, Darktrace AI successfully detected and thwarted a thread hijacking attack in real-time, effectively preventing potential email account compromise and data exfiltration. The attack employed a covert email rule that redirected messages away from the intended recipient, highlighting the sophisticated nature of such threats.
Experts in the field of cybersecurity have noted a concerning increase in thread hijacking incidents, a method employed by cybercriminals to infiltrate email communications and gain access to sensitive information. This approach is particularly dangerous as it often goes unnoticed by standard security protocols and human oversight.
During a thread hijacking attack, perpetrators gain unauthorized access to an individual’s email account, allowing them to monitor ongoing conversations and interject themselves into dialogues between users or organizations. This exploitation of trust within established email threads is a hallmark of the technique.
Recently, Darktrace’s AI technology detected a thread hijacking attempt aimed at a prominent organization. In this instance, the attack began with an email sent to a Software-as-a-Service (SaaS) user just hours before the creation of a dubious email rule. This email was purportedly a response to ongoing discussions concerning tax and payment matters. The AI’s ability to identify this behavior as anomalous enabled a swift response. The hidden rule was designed to reroute specific messages, obscuring the attacker’s actions from the target.
Details of the Attack
According to insights shared by Darktrace, the infiltration of the email account appeared to stem from phishing, malware, or the exploitation of weak passwords. Once inside, the attacker monitored the user’s email threads for any ongoing discussions that could be exploited. They then maliciously inserted themselves into conversations by replying to existing emails, which, due to appearing to originate from a trusted user, effectively bypassed many traditional cybersecurity defenses.
The attackers set up a new mailbox rule to forward certain emails to an archive, making it difficult for the victim to detect the malicious activity occurring. Leveraging the trust established in the ongoing conversation, the cybercriminal attempted to manipulate the user into clicking on harmful links or disclosing sensitive data.
“This evasion technique is typically used to move malicious communications to less monitored folders, ensuring that the legitimate account holder remains unaware of replies to phishing efforts or other harmful messages.”
Darktrace
Darktrace’s Swift Response
On August 8, 2024, Darktrace’s Self-Learning AI recognized the anomaly related to a suspiciously named mailbox rule, prompting an immediate response from the company’s RESPOND tool. This tool temporarily disabled the compromised SaaS user’s account for 24 hours, halting further escalation of the threat.
In addition, a Proactive Threat Notification was dispatched to the Darktrace Security Operations Center (SOC), enabling a thorough investigation of the incident and timely communication with the affected client. This occurrence underscores the critical role of advanced threat detection and response systems like Darktrace in safeguarding organizations against the evolving landscape of cyber threats such as thread hijacking.
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Increasingly, organizations need to understand the relevant tactics used in such cyberattacks. The MITRE ATT&CK framework could categorize the actions taken during this incident under initial access, persistence, and credential access. Understanding these attack vectors can enhance the preparedness of businesses against future threats.
In conclusion, as cyber threats continue to innovate, it is imperative for business owners to remain vigilant and proactive in their cybersecurity measures to protect against such sophisticated tactics.
