Detecting Vendor Email Compromise in Supply Chain Attacks
24
Mar 2021
Learn how Antigena Email stopped a supply chain attack by identifying a behavioral shift in the emails, while still allowing legitimate traffic through.
Supply chain account takeover – also known as Vendor Email Compromise — is the single most pressing issue facing email security at the moment. There has been a wave of high-profile supply chain attacks recently and this trend will only increase over 2021 as cyber-criminals continue to find success in such methods. Traditional security tools are powerless to stop such attacks: since the malicious emails come from trusted partners and suppliers, they slip through the gateway.
The recent SolarWinds cyber-attack shows just how devastating a supply chain compromise can be. Business partnerships are more complex than ever, which means that a single breach can affect dozens of organizations at all levels of a global supply chain, from small local companies to government departments.
This blog examines a compromised third-party provider which sent malicious emails to a customer trialing Antigena Email. Despite the emails coming from a trusted source, the AI technology recognized a behavioral shift – that they were anomalous when compared with the previous behavior of the sender. When the contact realized their account had been compromised and issued a warning via email to their regular contacts, Antigena recognized these emails as benign. But as the attacker continued sending emails of a malicious nature on their account, those threatening emails, which bypassed the company’s other security tools, were held back by Darktrace.
Supply chain compromise
Let’s set the scene. The company in question is one of the world’s largest beverage suppliers with around 15,000 email users alone. It has a sprawling global supply chain with many partners and trusted vendors. After one of these third parties was compromised, malicious actors sent phishing emails across the supply chain to compromise as many organizations as they could. Our beverage company was one of the main targets.
The trusted relationship with the third party can be seen through Darktrace’s Email tags, which were applied to the previous legitimate emails sent in from the supplier.
Shortly after this legitimate email was seen, a wave of new emails came in from the same account. Using this authentic traffic to their advantage, the attacker successfully evaded other tools and blended into legitimate communications. In supply chain attacks, such camouflage is key to a successful compromise.
However, due to slight changes in the behavior of the sender when compared with their previous history, Darktrace was able to identify that the account had been compromised, shown by the Out of Character and Suspicious Link tags.
Darktrace’s AI detected a range of anomalies, including:
the source of the email;
the nature of the links and their association with the company;
the language and intention of the email body.
These extremely subtle shifts in email can only be detected by using Darktrace’s sophisticated unsupervised machine learning approach. By understanding how the user typically acts and interacts with their peers and other organizations, Darktrace’s AI is able to identify anomalous behavior that indicates account takeover and impersonation.
Attack breakdown: Doubting the trustworthy
In the emails, there was a link directing the user to a legitimate file storage site (‘canva.com’), which was being used to host a malicious payload. This tactic is commonly used by cyber-criminals to bypass legacy security gateways, because traditional gateways fail to defend against malicious file storage links using reputation checks, since the domains themselves are legitimate.
Antigena Email, however, identified that this email did not belong and flagged the email as 100% anomalous. The figure below shows three of the malicious emails, and the scores assigned to them by Antigena Email’s machine learning. The top email is the supplier emailing the company legitimately, to warn of the compromised account. Despite arriving shortly after the malicious emails, the email was given only a 31% threat score, with no actions suggested. This proves just how valuable Antigena Email is not only in stopping the bad emails, but also in accurately identifying benign emails – ensuring it does not interfere with legitimate communication.
Antigena Email’s action of choice was to hold the emails back from the inbox entirely, protecting the recipient from any potential solicitation or attempt to take communications to a less secure platform.
Blind trust: The rise of supply chain attacks
This year will undoubtedly see the highly lucrative supply chain fraud continue to rise, as cyber-criminals focus on the weakest links and target partners and suppliers to gain a foothold in a range of organizations. In fact, it is likely that supply chain attacks will become more common than CEO fraud this year. Whereas the C-suite are often well protected by vigilant security teams, third parties offer a plethora of ways into a company. Security teams are blind to third-party environments and gateways rarely flag emails which come from legitimate sources.
Antigena Email is the only email security technology which looks at each individual email in the wider context of the organization, the recipient, and past interactions with the sender, stopping anomalous emails sent with malicious intent, no matter who has sent them.
Oops! Something went wrong while submitting the form.
Newsletter
Stay ahead of threats with the Darktrace blog newsletter
Get the latest insights from the cybersecurity landscape, including threat trends, incident analysis, and the latest Darktrace product developments – delivered directly to your inbox, monthly.
Thanks, your request has been received
A member of our team will be in touch with you shortly.
Oops! Something went wrong while submitting the form.
Inside the SOC
Darktrace cyber analysts are world-class experts in threat intelligence, threat hunting and incident response, and provide 24/7 SOC support to thousands of Darktrace customers around the globe. Inside the SOC is exclusively authored by these experts, providing analysis of cyber incidents and threat trends, based on real-world experience in the field.
Author
Dan Fein
VP, Product
Based in New York, Dan joined Darktrace’s technical team in 2015, helping customers quickly achieve a complete and granular understanding of Darktrace’s product suite. Dan has a particular focus on Darktrace/Email, ensuring that it is effectively deployed in complex digital environments, and works closely with the development, marketing, sales, and technical teams. Dan holds a Bachelor’s degree in Computer Science from New York University.
A snake in the net: Defending against AiTM phishing threats and Mamba 2FA
What are Adversary-in-the-Middle (AiTM) phishing kits?
Phishing-as-a-Service (PhaaS) platforms have significantly lowered the barriers to entry for cybercriminals, enabling a new wave of sophisticated phishing attacks. Among the most concerning developments in this landscape is the emergence of Adversary-in-the-Middle (AiTM) phishing kits, which enhance traditional phishing tactics by allowing attackers to intercept and manipulate communications in real-time. The PhaaS marketplace offers a wide variety of innovative capabilities, with basic services starting around USD 120 and more advanced services costing around USD 250 monthly [1].
These AiTM kits are designed to create convincing decoy pages that mimic legitimate login interfaces, often pre-filling user information to increase credibility. By acting as a man-in-the-middle, attackers can harvest sensitive data such as usernames, passwords, and even multi-factor authentication (MFA) tokens without raising immediate suspicion. This capability not only makes AiTM attacks more effective but also poses a significant challenge for cybersecurity defenses [2].
Mamba 2FA is one such example of a PhaaS strain with AiTM capabilities that has emerged as a significant threat to users of Microsoft 365 and other enterprise systems. Discovered in May 2024, Mamba 2FA employs advanced AiTM tactics to bypass MFA, making it particularly dangerous for organizations relying on these security measures.
What is Mamba 2FA?
Phishing Mechanism
Mamba 2FA employs highly convincing phishing pages that closely mimic legitimate Microsoft services like OneDrive and SharePoint. These phishing URLs are crafted with a specific structure, incorporating Base64-encoded parameters. This technique allows attackers to tailor the phishing experience to the targeted organization, making the deception more effective. If an invalid parameter is detected, users are redirected to a benign error page, which helps evade automated detection systems [5].
Real-Time Communication
A standout feature of Mamba 2FA is its use of the Socket.IO JavaScript library. This library facilitates real-time communication between the phishing page and the attackers' backend servers. As users input sensitive information, such as usernames, passwords, and MFA tokens on the phishing site, this data is immediately relayed to the attackers, enabling swift unauthorized access [5].
Multi-Factor Authentication Bypass
Mamba 2FA specifically targets MFA methods that are not resistant to phishing, such as one-time passwords (OTPs) and push notifications. When a user enters their MFA token, it is captured in real-time by the attackers, who can then use it to access the victim's account immediately. This capability significantly undermines traditional security measures that rely on MFA for account protection.
Infrastructure and Distribution
The platform's infrastructure consists of two main components: link domains and relay servers. Link domains handle initial phishing attempts, while relay servers are responsible for stealing credentials and completing login processes on behalf of the attacker. The relay servers are designed to mask their IP addresses by using proxy services, making it more difficult for security systems to block them [3].
Evasion Techniques
To evade detection by security tools, Mamba 2FA employs several strategies:
Sandbox Detection: The platform can detect if it is being analyzed in a sandbox environment and will redirect users to harmless pages like Google’s 404 error page.
Dynamic URL Generation: The URLs used in phishing attempts are frequently rotated and often short-lived to avoid being blacklisted by security solutions.
HTML Attachments: Phishing emails often include HTML attachments that appear benign but contain hidden JavaScript that redirects users to the phishing page [5].
Darktrace’s Coverage of Mamba 2FA
Starting in July 2024, the Darktrace Threat Research team detected a sudden rise in Microsoft 365 customer accounts logging in from unusual external sources. These accounts were accessed from an anomalous endpoint, 2607:5500:3000:fea[::]2, and exhibited unusual behaviors upon logging into Software-as-a-Service (SaaS) accounts. This activity strongly correlates with a phishing campaign using Mamba 2FA, first documented in late June 2024 and tracked as Mamba 2FA by Sekoia [2][3].
Darktrace / IDENTITY was able to identify the initial stages of the Mamba 2FA campaign by correlating subtle anomalies, such as unusual SaaS login locations. Using AI based on peer group analysis, it detected unusual behavior associated with these attacks. By leveraging Autonomous Response actions, Darktrace was able to neutralize these threats in every instance of the campaign detected.
On July 23, a SaaS user was observed logging in from a rare ASN and IP address, 2607:5500:3000:fea::2, originating from the US and successfully passed through MFA authentication.
Almost an hour later, the SaaS user was observed logging in from another suspicious IP address, 45.133.172[.]86, linked to ASN AS174 COGENT-174. This IP, originating from the UK, successfully passed through MFA validation.
Following this unusual access, the SaaS user was notably observed reading emails and files that could contain sensitive payment and contract information. This behavior suggests that the attacker may have been leveraging contextual information about the target to craft further malicious phishing emails or fraudulent invoices. Subsequently, the user was detected creating a new mailbox rule titled 'fdsdf'. This rule was configured to redirect emails from a specific domain to the 'Deleted Items' folder and automatically mark them as read.
Implications of Unusual Email Rules
Such unusual email rule configurations are a common tactic employed by attackers. They often use these rules to automatically forward emails containing sensitive keywords—such as "invoice”, "payment", or "confidential"—to an external address. Additionally, these rules help conceal malicious activities, keeping them hidden from the target and allowing the attacker to operate undetected.
Blocking the action
A few minutes later, the SaaS user from the unusual IP address 45.133.172[.]86 was observed attempting to send an email with the subject “RE: Payments.” Subsequently, Darktrace detected the user engaging in activities that could potentially establish persistence in the compromised account, such as registering a new authenticator app. Recognizing this sequence of anomalous behaviors, Darktrace implemented an Autonomous Response inhibitor, disabling the SaaS user for two hours. This action effectively contained potential malicious activities, such as the distribution of phishing emails and fraudulent invoices, and gave the customer’s security team the necessary time to conduct a thorough investigation and implement appropriate security measures.
In another example from mid-July, similar activities related to the campaign were observed on another customer network. A SaaS user was initially detected logging in from the unusual external endpoint 2607:5500:3000:fea[::]2.
A few minutes later, in the same manner as demonstrated in the previous case, the actor was observed logging in from another rare endpoint, 102.68.111[.]240. However, this time it was from a source IP located in Lagos, Nigeria, which no other user on the network had been observed connecting from. Once logged in, the SaaS user updated the settings to "User registered Authenticator App with Notification and Code," a possible attempt to maintain persistence in the SaaS account.
Based on unusual patterns of user behavior, a Cyber AI Analyst Incident was also generated, detailing all potential account hijacking activities. Darktrace also applied an Autonomous Response action, disabling the user for over five hours. This swift action was crucial in preventing further unauthorized access, potential data breaches and further implications.
Since the customer had subscribed to Darktrace Security Operations Centre (SOC) services, Darktrace analysts conducted an additional human investigation confirming the account compromise.
How Darktrace Combats Phishing Threats
The initial entry point for Mamba 2FA account compromises primarily involves phishing campaigns using HTML attachments and deceptive links. These phishing attempts are designed to mimic legitimate Microsoft services, such as OneDrive and SharePoint, making them appear authentic to unsuspecting users. Darktrace / EMAIL leverages multiple capabilities to analyze email content for known indicators of phishing. This includes looking for suspicious URLs, unusual attachments (like HTML files with embedded JavaScript), and signs of social engineering tactics commonly used in phishing campaigns like Mamba 2FA. With these capabilities, Darktrace successfully detected Mamba 2FA phishing emails in networks where this tool is integrated into the security layers, consequently preventing further implications and account hijacks of their users.
Mamba 2FA URL Structure and Domain Names
The URL structure used in Mamba 2FA phishing attempts is specifically designed to facilitate the capture of user credentials and MFA tokens while evading detection. These phishing URLs typically follow a pattern that incorporates Base64-encoded parameters, which play a crucial role in the operation of the phishing kit.
The URLs associated with Mamba 2FA phishing pages generally follow this structure [6]:
https://{domain}/{m,n,o}/?{Base64 string}
Below are some potential Mamba 2FA phishing emails, with the Base64 strings already decoded, that were classified as certain threats by Darktrace / EMAIL. This classification was based on identifying multiple suspicious characteristics, such as HTML attachments containing JavaScript code, emails from senders with no previous association with the recipients, analysis of redirect links, among others. These emails were autonomously blocked from being delivered to users' inboxes.
Conclusion
The rise of PhaaS platforms and the advent of AiTM phishing kits represent a concerning evolution in cyber threats, pushing the boundaries of traditional phishing tactics and exposing significant vulnerabilities in current cybersecurity defenses. The ability of these attacks to effortlessly bypass traditional security measures like MFA underscores the need for more sophisticated, adaptive strategies to combat these evolving threats.
By identifying and responding to anomalous activities within Microsoft 365 accounts, Darktrace not only highlights the importance of comprehensive monitoring but also sets a new standard for proactive threat detection. Furthermore, the autonomous threat response capabilities and the exceptional proficiency of Darktrace / EMAIL in intercepting and neutralizing sophisticated phishing attacks illustrate a robust defense mechanism that can effectively safeguard users and maintain the integrity of digital ecosystems.
Credit to Patrick Anjos (Senior Cyber Analyst) and Nahisha Nobregas (Senior Cyber Analyst)
Appendices
Darktrace Model Detections
SaaS / Access / M365 High Risk Level Login
SaaS / Access / Unusual External Source for SaaS Credential Use
SaaS / Compromise / Login From Rare Endpoint While User Is Active
SaaS / Compliance / M365 Security Information Modified
SaaS / Compromise / Unusual Login and New Email Rule
Protecting your hybrid cloud: The future of cloud security in 2025 and beyond
Cloud security in 2025
The future of cybersecurity is being shaped by the rapid adoption of cloud technologies.
As Gartner reports, “By 2027, more than 70% of enterprises will use industry cloud platforms to accelerate their business initiatives, up from less than 15% in 2023” [1].
As organizations continue to transition workloads and sensitive data to cloud environments, the complexity of securing distributed infrastructures grows. In 2025, cloud security will need to address increasingly sophisticated threats with innovative approaches to ensure resilience and trust.
Emerging threats in cloud security:
Supply chain attacks in the cloud: Threat actors are targeting vulnerabilities in cloud networks, including third-party integrations and APIs. These attacks can have wide-spanning impacts, jeopardizing data security and possibly even compromising multiple organizations at once. As a result, robust detection and response capabilities are essential to identify and neutralize these attacks before they escalate.
Advanced misconfiguration exploits: Misconfigurations remain a leading cause of cloud security breaches. Attackers are exploiting these vulnerabilities across dynamic infrastructures, underscoring the need for tools that provide continuous compliance validation in the future of cloud computing.
Credential theft with evolving Tactics, Techniques, and Procedures (TTPs): While credential theft can result from phishing attacks, it can also happen through other means like malware, lateral movement, data breaches, weak and reused passwords, and social engineering. Adversarial innovation in carrying out these attacks requires security teams to use proactive defense strategies.
Insider threats and privilege misuse: Inadequate monitoring of Identity and Access Management (IAM) in cloud security increases the risk of insider threats. The adoption of zero-trust architectures is key to mitigating these risks.
Threats exploiting dynamic cloud scaling: Attackers take advantage of the dynamic nature of cloud computing, leveraging ephemeral workloads and autoscaling features to evade detection. This makes adaptive and AI-driven detection and response critical because it can more easily parse behavioral data that would take human security teams longer to investigate.
Where the industry is headed
In 2025, cloud infrastructures will become even more distributed and interconnected. Multi-cloud and hybrid models will dominate, so organizations will have to optimize workloads across platforms. At the same time, the growing adoption of edge computing and containerized applications will decentralize operations further. These trends demand security solutions that are agile, unified, and capable of adapting to rapid changes in cloud environments.
Emerging challenges in securing cloud environments
The transition to highly distributed and dynamic cloud ecosystems introduces the following key challenges:
Limited visibility As organizations adopt multiple platforms and services, gaining a unified view of cloud architectures becomes increasingly difficult. This lack of visibility makes it unclear where sensitive data resides, which identities can access it and how, and if there are potential vulnerabilities in configurations and API infrastructure. Without end-to-end monitoring, detecting and mitigating threats in real time becomes nearly impossible.
Complex environments The blend of public, private, and hybrid clouds, coupled with diverse service types (SaaS, PaaS, IaaS), creates a security landscape rife with configuration challenges. Each layer adds complexity, increasing the risk of misconfigurations, inconsistent policy enforcement, and gaps in defenses – all of which attackers may exploit.
Dynamic nature of cloud Cloud infrastructures are designed to scale resources on demand, but this fluidity poses significant challenges to threat detection and incident response. Changes in configurations, ephemeral workloads, and fluctuating access points mean that on-prem network security mindsets cannot be applied to cloud security and many traditional cloud security approaches still fall short in addressing threats in real time.
Looking forward: Protecting the cloud in 2025 and beyond
Addressing these challenges requires innovation in visibility tools, AI-driven threat detection, and policy automation. The future of cloud security hinges on solutions that adapt to complexity and scale, ensuring organizations can securely navigate the growing demands of cloud-first operations.
Unlike supervised ML, which relies on labeled datasets, unsupervised ML identifies patterns and deviations in data without predefined rules, making it particularly effective in dynamic and unpredictable environments like the cloud. By analyzing the baseline behavior in cloud environments, such as typical user activity, network traffic, and resource utilization, unsupervised ML and supporting models can identify behavioral deviations linked to suspicious activity like unusual login times, irregular API calls, or unexpected data transfers, therefore flagging them as potential threats.
Learn more about how multi-layered ML improves real-time cloud detection and response in the data sheet “AI enhances cloud security.”
Agent vs. Agentless deployment
The future of cloud security is increasingly focused on combining agent-based and agentless solutions to address the complexities of hybrid and multi-cloud environments.
This integrated approach enables organizations to align security measures with the specific risks and operational needs of their assets, ensuring comprehensive protection.
Agent-based systems provide deep monitoring and active threat mitigation, making them ideal for high-security environments like financial services and healthcare, where compliance and sensitive data require stringent safeguards.
Meanwhile, agentless systems offer broad visibility and scalability, seamlessly covering dynamic cloud resources without the need for extensive deployment efforts.
Together, a combination of these approaches ensures that all parts of the cloud environment are protected according to their unique risk profiles and functional requirements.
The growing adoption of this strategy highlights a shift toward adaptive, scalable, and efficient security solutions, reflecting the priorities of a rapidly evolving cloud landscape.
Shifting responsibilities: security teams must get more comfortable with cloud mindsets
Traditionally, many organizations left cloud security to dedicated cloud teams. However, it is becoming more and more common for security teams to take on the responsibilities of securing the cloud. This is also true of organizations undergoing cloud migration and spinning up cloud infrastructure for the first time.
Notably, the usual approaches to other types of cybersecurity can’t be applied the exact same way to the cloud. With the inherent dynamism and flexibility of the cloud, the necessary security mindset differs greatly from those for the network or datacenters, with which security teams may be more familiar.
For example, IAM is both critical and distinct to cloud computing, and the associated policies, rules, and downstream impacts require intentional care. IAM rules not only govern people, but also non-human entities like service accounts, API keys, and OAuth tokens. These considerations are unique to cloud security, and established teams may need to learn new skills to reduce security gaps in the cloud.
The importance of visibility: The future of network security in the cloud
As organizations transition to cloud environments, they still have much of their data in on-premises networks, meaning that maintaining visibility across both on-premises and cloud environments is essential for securing critical assets and ensuring seamless operations. Without a unified security strategy, gaps between these infrastructures and the teams which manage them can leave organizations vulnerable to cyber-attacks.
Shared visibility across both on-premises and cloud environments unifies SecOps and DevOps teams, enabling them to generate actionable insights and develop a cohesive approach. This alignment helps confidently mitigate risks across the cloud and network while streamlining workflows and accelerating the cloud migration journey—all without compromising security or operational continuity.