Detecting Malicious Email Activity & AI Impersonating
Discover how two different phishing attempts from some known and unknown senders used a payroll diversion and credential sealing box link to harm users.
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.
Written by
Isabelle Cheong
Cyber Security Analyst
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11
Apr 2023
Social engineering has become widespread in the cyber threat landscape in recent years, and the near-universal use of social media today has allowed attackers to research and target victims more effectively. Social engineering involves manipulating users to carry out actions such as revealing sensitive information like login credentials or credit card details. It can also lead to user account compromises, causing huge disruption to an organization’s digital estate.
As people use social media platforms not only for personal reasons, but also for business purposes, attackers gain information they can exploit in social engineering attacks. For example, a threat actor may attempt to impersonate a known individual or legitimate service to take advantage of a user’s established trust. This is a highly successful method of social engineering because mimicking known contacts makes it difficult for traditional security tools that rely on deny-lists to detect the attack.
In October 2022, Darktrace identified and responded to two separate malicious email campaigns in which threat actors attempted to impersonate known contacts in an effort to compromise customer devices. As it learns the normal behavior of every user in the email system, Darktrace was able to instantly detect these threats and mitigate them autonomously, preventing significant disruption to the customer networks.
Payroll Diversion Fraud Attempt Impersonating a Former Employee
While a customer in the Canadian energy sector was trialing Darktrace in October 2022, Darktrace/Email™ identified a suspicious email seemingly sent from an employee within the organization. The email was sent to the Senior Director of Human Resources (HR) with a subject line of “Change in payroll Direct Deposit.” The email requested a change in bank account information for an employee. However, Darktrace recognized that the sender was using a free mail address that contained random letters, indicating it may have been algorithmically generated. Since this incident occurred during a trial, Darktrace/Email was not configured to take action. Otherwise, it would have prevented the email from landing in the inbox. In this case though, the email went through, bypassing all other security tools in place.
Although the email was from an unknown sender, the HR director believed the email could have been legitimate as the employee who appeared to be the sender had left the organization seven days prior and no longer had access to their corporate email account. However, after reviewing it in the Darktrace/Email dashboard, the customer grew suspicious and contacted the former employee directly to verify if the request was legitimate. The former employee validated the suspicions by confirming they had sent no such email.
Further investigation by the customer revealed that the former employee had been vocal about their departure on various social media platforms. This gave threat actors valuable information to believably impersonate the former employee and defraud the organization.
Such attempts to target organizations’ HR departments and divert payroll are common tactics for cyber-criminals and are often identified by Darktrace/Email across the customer base. Darktrace/Email is able to instantly identify the indicators associated with these spoofing attempts and immediately bring them to the attention of the customer’s security team.
Using Legitimate File Sharing Service to Share a Phishing Link
On October 7, 2022, a customer in the Singaporean construction sector was targeted by a phishing campaign attempting to impersonate a law firm known to the organization. Almost 200 employees received an email with the subject line “Accepted: Valuation Agreement.”
Figure 1: Sample of an UI view of the message held showing anomaly indicators, history, association, and validation.
Four days earlier, Darktrace observed communication between another email address associated with the law firm and an employee of the customer. Darktrace/Email noted that it was the first time this correspondent had sent emails to the customer.
Figure 2: Metrics showing how well the sender’s domain is known within the digital environment.
The emails contained a highly unusual link to a file sharing service, (hxxps://ssvilvensstokes[.]app[.]box[.]com/notes), hidden behind the text “PREVIEW OR PRINT COPY OF DOCUMENT HERE.” Darktrace analysts investigated this event further and found that around 30 similar URLs had been identified as suspicious using OSINT security tools in October 2022, suggesting the customer was not the only target of this phishing campaign.
Figure 3: Preview of the phishing email’s body.
Figure 4: Darktrace’s evaluation of the link contained in the phishing email.
Additional OSINT work revealed that the link directed to a website which appeared to host a PDF file named “Valuation Agreement.” The recipient would then be prompted to follow another link (hulking-citrine-krypton[.]glitch[.]me), again hidden behind the text “OPEN OR ACCESS DOCUMENT HERE” to view the file. Subsequently, the user would be prompted to enter their Microsoft 365 credentials.
Figure 5: The page displayed when the phishing link was clicked, viewed in a sandbox environment.
Figure 6: Example of a page shown when recipient clicks the second link, accessing “hulking-citrine-krypton[.]glitch[.]me”.
This page contained the text “This document has been scanned for viruses by Norton Antivirus Security.” This is another example of threat actors’ employing social engineering techniques by impersonating well-known brands, such as established security vendors, to gain the trust of users and increase their likelihood of success.
It is highly probable that a real employee of the law firm had their account hijacked and that a malicious actor was exploiting it to send out these phishing emails en masse as part of a supply chain attack. In such cases, malicious actors rely on their targets’ trust of known contacts to not question departures from their normal conversations.
Darktrace was able to instantly detect multiple anomalies in these emails, despite the fact that they were seemingly sent by known correspondents. The activity detected automatically triggered model breaches associated with unexpected and visually prominent links. As a result, Darktrace/Email responded by locking the link, stopping users from being able to click it.
Darktrace subsequently identified additional emails from this sender attempting to target other recipients within the company, triggering the model breaches associated with a surge in email sending indicative of a phishing campaign. In response, Darktrace/Email autonomously acted and filed these emails as junk. As more emails were detected across the customer’s environment, the anomaly score of the sender increased and Darktrace ultimately held back over 160 malicious emails, safeguarding recipients from potential account compromise.
The following Darktrace/Email models were breached throughout the course of this phishing campaign:
Unusual/Sender Surge
Unusual/Undisclosed Recipients
Antigena Anomaly
Association/Unlikely Recipient Association
Link/Low Link Association
Link/Visually Prominent Link
Link/Visually Prominent Link Unexpected For Sender
Unusual/New Sender Wide Distribution
Unusual/Undisclosed Recipients + New Address Known Domain
Conclusion
Social engineering plays a role in many of the major threats challenging current email cyber security, as attackers can use it to manipulate users into transferring money, revealing credentials, clicking malicious links, and more.
The above threat stories happened before language generating AI became mainstream with the release of ChatGPT in December 2022. Now, it is even easier for malicious actors to generate sophisticated social engineering emails. By using social media posts as input, social engineering emails written by generative AI can be highly targeted and produced at scale. They often avoid the flags users are trained to look for, like poor grammar and spelling mistakes, and can hide payloads or forgo them entirely.
To mitigate the risk of possible social engineering attempts, it is recommended that organizations implement social media policies that advise employees to be cautious of what they post online and enact procedures to verify if fund transfer requests are legitimate.
Yet these policies are not enough on their own. Darktrace/Email can identify suspicious email traits, whether an email is sent from a known correspondent or an unknown sender. With Self-Learning AI, it knows an organization’s users better than any impersonator could. In this way, Darktrace/Email detects anomalies within emails and neutralizes malicious components at machine-speed, stopping attacks at their earliest stages, before employees fall victim.
Appendices
List of Indicators of Compromise (IoCs)
Domain:
hxxps://ssvilvensstokes[.]app[.]box[.]com/notes/*?s=* - 1st external link (seen in email)
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.
Darktrace / EMAIL Expands Behavioral Defense Across Email and Collaboration Workflows
New capabilities help employees understand suspicious content, give administrators more control over sensitive data, and show security teams where risky workflows sit across the organization.
Journey of a Threat: How Multi-Layered AI Works in Darktrace / EMAIL
Follow a malicious email as it moves through Darktrace / EMAIL’s multi-layered AI system, from raw data to final decision. Each layer works together to detect threats, understand intent, and take autonomous action.
Hiding in Plain Sight: Uncovering a Multi-Stage Ransomware Attack Through Behavioral Detection
Why ransomware has changed
Ransomware attacks have continued to increase globally, with 698 incidents reported in May 2026, representing a 48% rise compared to 472 incidents in May 2025 [1]. At the same time, the ransomware landscape is evolving. Several major ransomware groups, including LockBit [2], have been disrupted by successful joint law enforcement operations, resulting in a shift away from a small number of dominant actors towards a more fragmented and distributed ecosystem. This is increasingly composed of smaller groups who play a specialized role in the attack, such as initial access brokers, affiliates or developers.
As a result, ransomware tactics, techniques, and procedures (TTPs) are becoming more diverse and less predictable. On top of this, adversaries are leveraging native tools and legitimate penetration testing frameworks to evade detection. Anomaly-based detection is therefore critical to identify pre-ransomware activity, rather than relying on signatures associated with a handful of well-known ransomware groups.
As these attacks often unfold over several days, there is a critical window for defenders to act. In this context, behavioral-based detection plays a vital role in identifying suspicious pre-ransomware activity, and enabling early intervention before encryption or exfiltration occurs.
Inside a modern ransomware intrusion
In early 2026, Darktrace detected activity within a customer’s environment related to a multi-stage ransomware intrusion from the initial compromise. This activity does not appear to be attributable to a specific ransomware group, and no known ransomware payload was observed until the final stage.
The attack aligns with a broader industry trend in which compromised virtual private network (VPN) credentials are used as an entry point, followed by rapid internal reconnaissance and lateral movement using legitimate administrative tools. This growing preference for native tools and legitimate frameworks in cyber-attacks illustrates that it is increasingly unreliable to depend solely on traditional indicators of compromise such as known malware signatures or exploit detection.
The intrusion also involved the use of Sliver, an open-source adversary emulation framework, which is increasingly observed in real-world attacks. Originally designed for penetration testing and red teaming, Sliver has gained traction among threat actors as a stealthier alternative to more heavily signatured frameworks such as Cobalt Strike. As a legitimate framework, its use further complicates detection for security tools that rely on known malicious signatures.
Darktrace’s detection of a ransomware event in a customer’s environment
The initial compromise appears to have occurred via compromised credentials used over the VPN shortly before, or at the onset of the first indicators of suspicious activity. While it remains unclear as to how or when the threat actors gained access to these credentials, the use of initial access brokers (IABs) is a common feature of modern ransomware operations. This suggests that access to the environment may have been established several days or weeks beforehand.
The intrusion unfolded over three days, presenting multiple opportunities for early detection and intervention before ransomware deployment. The attack progressed through a compressed but structured sequence: initial access and reconnaissance were completed within hours, followed by privilege escalation and lateral movement the next day, and culminating in data exfiltration and encryption shortly thereafter. Throughout each stage, distinct behavioral anomalies emerged across the network providing clear indicators of malicious activity well before the ransomware was deployed.
While Darktrace’s Autonomous Response capability was enabled within the customer’s environment, it was not fully configured across the impacted devices, allowing the attack to progress to ransomware deployment. Had Autonomous Response been fully deployed across the affected systems, it could have taken targeted action against the earliest stages of malicious activity, potentially disrupting the intrusion before it escalated.
Figure 1: Timeline of the attack progression.
Day 1: Reconnaissance and privilege escalation
The threat actor gained access via compromised VPN credentials and initiated internal reconnaissance. Darktrace detected anomalous scanning behavior, including unusual port scanning activity and widespread network enumeration.
Specifically, Darktrace detected a high volume of east-west scanning activity across a broad range of ports, with TCP connections targeting ports 21, 80, 445, 4899 and 8080. Associated URIs suggested the use of Nmap, a widely used penetration testing tool. This highlights how attackers often leverage legitimate penetration testing tools for malicious reconnaissance, enabling them to blend into normal network activity and evade traditional signature-based detection methods.
Figure 2: Darktrace's detection of a sharp increase in anomalous internal connections, triggering multiple high-severity model alerts associated with reconnaissance activity.
Several devices were observed using administrative credentials to carry out privileged actions in a manner that was highly anomalous for the environment. This activity was accompanied by behavior consistent with SMB authentication scanning, suggesting efforts to identify and access additional systems. As the activity intensified, an increasing number of devices became involved, signalling lateral movement and further spread across the network.
Darktrace also identified privilege escalation through active directory (AD) replication abuse, specifically via the drsuapi::DRSGetNCChanges function. This technique allows an attacker with sufficient privileges to request directory replication data from a domain controller (DC), enabling them to extract credentials, including password hashes, without directly interacting with user accounts. Commonly associated with ‘DCSync’ attacks, this technique is frequently used to obtain highly privileged credentials and enable further escalation within an environment.
Figure 3: Darktrace’s detection of anomalous AD replication activity indicative of privilege escalation.
This activity was seen alongside the use of the now obsolete SMBv1, repeated NTLM authentication attempts using multiple variations of ‘Administrator’ credentials, reverse DNS scanning, and large-scale network scanning. Darktrace observed widespread use of SMBv1 across the customer’s environment, exposing a significant security weakness. As a legacy protocol with well-documented weaknesses, SMBv1 can be exploited to facilitate lateral movement, allowing the attackers to expand their access following initial compromise.
Day 3: Lateral Movement, Command & Control, and Exfiltration
Two days later, the attacker escalated privileges and expanded their foothold using living-off-the-land (LOTL) techniques such as PSExec, WMI, and RDP. Concurrently, Darktrace identified command-and-control (C2)-style communications consistent with the Sliver framework, alongside rare outbound connections to cloud infrastructure indicating potential data exfiltration. The volume and severity of observed activity increased as attack behavior intensified.
The device was observed conducting extensive lateral movement, leveraging LOTL techniques to evade detection. Activity included WMI execution (e.g. ExecQuery), DCE-RPC activity, SMB sessions and file writes, most of which were successful, as well as the deployment of PSEXESVC.exe via ADMIN$ shares and prolonged RDP sessions. Darktrace identified this behavior as highly anomalous for the environment. Such activity is commonly associated with the transfer of attacker tooling, remote command execution, and the establishment of persistent access across compromised systems.
Figure 4: Darktrace’s detection of a spike in RPC binding events indicative of potential lateral movement.
On the same day, Darktrace detected C2-style SSL communications originating from multiple internal devices to rare external endpoints. These connections exhibited anomalous characteristics, including invalid SSL certificates and repeated connection patterns resembling beaconing. Analysis of the observed JA3 fingerprint further linked the activity to Sliver, the adversary simulation framework referenced earlier, as the hash has previously been associated with Sliver-related infrastructure [3]. The use of this framework reflects a broader trend of attackers repurposing legitimate offensive security tools for stealthy C2 communications. Connections to 137[.]220[.]59[.]55 (ASN AS20473 AS-VULTR) indicated that the communications were likely routed via a virtual private server (VPS) hosted by Vultr. Attackers often utilize VPS infrastructure from legitimate cloud providers like Vultr to obscure their true origin, blend into benign traffic, and evade IP-based detection mechanisms [4].
Figure 5: Darktrace’s Cyber AI Analyst detection of two linked unusual connections to Vultr infrastructure.
Darktrace also observed a device initiating SSL connections to safedata.s3[.]wasabisys[.]com, an endpoint associated with Wasabi cloud storage. Darktrace recognized that neither the destination nor the associated IP address had previously been observed within the environment. More than 200 MB of data was subsequently uploaded externally to endpoints sharing the same JA3 client hash, indicating a sustained transfer session and potential data exfiltration to third-party storage. The apparent exfiltration prior to encryption is consistent with a double-extortion ransomware strategy.
Figure 6: Darktrace’s Cyber AI Analyst detection of more than 30 rare outbound connections to a Wasabi cloud storage endpoint, indicative of potential data exfiltration
Day 4: Encryption
The attack culminated in ransomware deployment, marking the transition from suspicious network activity to a business-impacting incident. Using SMB-based propagation, the threat actor encrypted thousands of files across the network, affecting multiple systems and disrupting normal operations. Throughout the encryption event, the legacy SMBv1 protocol was used extensively across multiple internal systems, resulting in a significant increase in newly encrypted files.
Figure 7: Darktrace’s detection of abnormal spikes in SMB activity and associated model alerts, indicative of ransomware encryption and propagation.
Darktrace’s Cyber AI Analyst automatically investigated and correlated the encryption activity and related events into a single incident narrative, providing the customer with real-time visibility into the attack while significantly reducing investigation time.
Figure 8: Darktrace’s Cyber AI Analyst’s investigation into the encryption activity. AI Analyst incident detailing example encryption activity in real time. Related events are automatically correlated and summarized into a clear narrative, reducing investigation time.
Defender action recommendations
What Could Have Stopped the Attack Earlier?
Although the attack ultimately resulted in ransomware deployment, there were multiple opportunities to detect, contain, and disrupt the intrusion before encryption occurred. The following actions could have significantly reduced the overall impact:
Detect and investigate indicators of reconnaissance and lateral movement
Unusual scanning
Active Directory replication anomalies consistent with DCSync activity
Anomalous use of native tools and processes indicative of LOTL attacks
Unusual use of common reconnaissance tools such as Nmap and NetScan
Contain compromised credentials and affected devices
Disable and reset compromised VPN credentials
Isolate devices performing anomalous scanning and lateral movement activity
Block suspicious external communications and data exfiltration
Use anomaly-based detection to detect and block repeated outbound connections to rare external infrastructure
Prevent data exfiltration to unauthorized cloud storage services such as Wasabi
Conclusion
The incident highlights the importance of anomaly-based detection, particularly against attacks that primarily use native or legitimate tools to evade traditional security measures. Darktrace identified suspicious activity from the first day of the compromise, providing multiple opportunities to disrupt the intrusion before it progressed to lateral movement and data exfiltration.
In this instance, detection was not the limiting factor; response time was. Prompt investigation and containment of devices exhibiting anomalous behavior could have prevented lateral movement, data exfiltration, and ultimately ransomware deployment.
As adversaries increasingly prioritize stealth over custom malware, relying instead on legitimate tools, valid credentials, and trusted infrastructure, traditional signature-based detection becomes less effective. Identifying subtle behavioral deviations early remains critical to disrupting attacks before they escalate into full-scale ransomware incidents.
Credit to Alexandra Evzona (Cyber Analyst), Priya Thapa (Senior Cyber Analyst) Edited by Ryan Traill (Content Manager)
Darktrace / EMAIL Expands Behavioral Defense Across Email and Collaboration Workflows
Email and collaboration tools do more than carry messages. They are where organizations approve payments, share sensitive data, reset credentials, and make thousands of everyday decisions. Increasingly, they are interfaces through which humans direct AI agents in their daily activity. Email, Slack and Teams are high volume, rich with sensitive data, and an easy place to hide malicious activity.
The opportunity isn’t lost on bad actors. Darktrace / EMAIL detected more than 32 million high-confidence phishing emails globally in 2025, and 70% of those messages passed DMARC authentication. Phishing is increasingly difficult to detect and familiar trust signals alone are not enough. People and security teams need to understand how a message fits the normal behavior of the sender, recipient, and organization. They also need to correlate activity across platforms to spot threats that span multiple channels.
To effectively secure against today’s evolved threats, security teams need to act at two levels: they need to help each employee make a safer decision ‘in the moment’, and they need to understand the wider patterns that may expose the business to risk.
Darktrace is introducing four new capabilities in Darktrace / EMAIL to address both challenges. The new features explain suspicious content more clearly to end users, strengthen the capabilities of Darktrace / Adaptive Human Defense with richer guidance, let organizations define their own patterns for detecting sensitive data in messages, and give security teams a process-level view of risk across email and collaboration workflows.
Darktrace / EMAIL Inbox Analysis highlights risky content within your emails
A warning is more useful when it explains what the user should look at. To help do that, we’ve expanded Darktrace / EMAIL’s Inbox Analysis Add-In to highlight potentially dangerous content within the body of emails that Darktrace / EMAIL flags as potentially suspicious or high risk.
The add-in can highlight language designed to create urgency, financial references, requests for payment, suspicious links, and content that is unusual for the sender. Each highlighted element includes a pop up that explains why it may be suspicious. Instead of asking an employee to accept a verdict without context, the analysis helps them examine the message and make a more informed decision.
Enhanced Just-In-Time Training Banners in Darktrace / Adaptive Human Defense
Enhanced Just-In-Time Training Banners build on the same principle. The banners now include a contextual header, actionable advice, and specific detection context. This gives employees more useful guidance at the point of risk without adding unnecessary information or cognitive load.
Together, the capabilities help turn a warning into a short learning moment. Employees can see what looks unusual, understand what action to take, and build their judgment.
Custom Sensitive Data Detection in Darktrace / EMAIL - Data Loss Prevention
Sensitive data is different for every business. Standard categories such as payment card details or government identifiers matter, but organizations also have their own customer codes, project names, research formats, account structures, and internal identifiers.
Custom Sensitive Data Detection in Darktrace / EMAIL - Data Loss Prevention allows administrators to write custom expressions for the data their organization needs to protect. Matched content can trigger existing model actions and data loss prevention (DLP) workflows, extending Darktrace's DLP capabilities.
This extends data loss detection beyond a fixed library of common data types. Security teams can apply controls to information that is sensitive in the context of their own organization and adapt those controls as the business changes.
Introducing Email and Collaboration Workflow Risk Posture Dashboards
Some of the most important risks are not isolated events. They are repeated ways of working that create an opening for error, misuse, or attack. For example, a payment request may be one suspicious message, but a recurring approval workflow that relies on weak verification is a business process risk.
The new Email and Collaboration Workflow Risk Posture Dashboard analyzes email and collaboration data across Email, Microsoft Teams, Slack and Zoom to provide a process-level view of risk in the organization. These may include financial authorization workflows, sensitive data sharing patterns, and activity that could expose credentials.
The dashboard brings these patterns into a view and provides actionable recommendations. This helps security teams determine where to investigate or strengthen controls, where ownership needs to be clarified, and where the business may need to change a risky process. It gives CISOs a clearer view of how human and communication risk is embedded in everyday operations, not only where individual alerts occur.
Behavior connects the individual decision to the wider risk
These capabilities build on Darktrace’s unique behavioral approach to security. We use Adaptive AI to learn how people and AI normally behave within an organization, creating the context needed to recognize when activity changes.
Within the Darktrace Behavioral Defense Platform, Darktrace / EMAIL helps protect people against phishing, account takeover, data exfiltration, and human risk across email and collaboration tools. The new capabilities extend that protection in both directions. They give employees clearer context for the decision in front of them, while giving security leaders a broader view of the workflows and behavior that create risk across the organization.
The result is not simply more alerts. It is a better understanding of why something is risky, what action to take, and where the organization can reduce risk before a familiar process becomes an easy route for an attacker.
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