Email Security: Darktrace's Approach to Safe New Contacts
Effective email security should provide full protection and keep business running smoothly. Learn about the security approach that Darktrace Email uses!
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
Mariana Pereira
VP, Field CISO
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19
Jul 2020
Antigena Email uniquely understands employees’ patterns of life, including how they behave and communicate, in order to identify anomalous behavior that it deems threatening and neutralize malicious emails in real time. This self-learning approach has enabled the technology to stop advanced attacks that other tools missed, including a Siemens impersonation attack, a QuickBooks scam, and a fraudulent Chase fraud alert.
But how does an AI-powered approach handle the case of the ‘unusual but benign’: an email from a new contact which is highly unusual, but non-threatening?
This blog follows an employee at a marketing agency that had deployed Darktrace across its entire digital estate. The employee, Roberta, had recently organized a virtual event, and was looking to send a thank you gift to the speakers who participated. She found Patch, a leading online supplier of plants perfect for the ‘clueless urban gardener’ that Roberta felt would be a good choice.
Figure 1: The webpage of Patch, a new supplier to the organization
After visiting the website and choosing the perfect gift, Roberta signed up for the Patch newsletter with her corporate email; this was a business expense after all.
A common source of frustration often arises when a team or an employee is trying to do new things, but are stopped by security policies that pre-define what they are allowed to do or who they can contact. Some email security vendors take the approach that only known correspondents or pre-approved domains can send emails to employees’ corporate emails. This principle, while effective at keeping out many spam and spoofing emails, will also block unusual but legitimate, and potentially important, emails from making their way into the inbox, leading to frustration.
Planting the seed
Thankfully for Roberta, Darktrace’s AI contextualizes email anomalies with an understanding of the user that looks beyond the inbox and draws insights from across employees’ digital footprint. A holistic understanding of both email and network traffic enabled the AI to recognize that Roberta had visited the Patchplants.com website and signed up for the newsletter. This prior event contextualized the subsequent email and allowed Darktrace to recognize that despite being anomalous and new, this email was legitimate and no action was necessary.
Figure 2: Darktrace’s Email Dashboard surfaces a high rarity score of 99
No other employee at the company had ever received mail from this domain, with Antigena Email giving the email a rarity score of 99. However, the brief interaction with the website helped the AI decide that even though this was a highly unusual domain, it was not a threat, and the email was promptly delivered.
Figure 3: The newsletter welcome email
The good, the bad and the ugly
This example demonstrates the importance of a security stack that can discern when unusual activity or an anomalous email is acceptable, and the value of user context and insights gathered across the digital ecosystem. New business often relies on new interactions that are difficult to write into security and policy rules, and so understanding the ‘unusual but benign’ is key so that businesses, like plants, can grow and thrive.
Darktrace’s AI can make these critical determinations based on its evolving understanding of the user and the business as a whole, stopping malicious emails and only the malicious emails.
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.
Vo1d malware first appeared in the wild in September 2024 and has since evolved into one of the most widespread Android botnets ever observed. This large-scale Android malware primarily targets smart TVs and low-cost Android TV boxes. Initially, Vo1d was identified as a malicious backdoor capable of installing additional third-party software [1]. Its functionality soon expanded beyond the initial infection to include deploying further malicious payloads, running proxy services, and conducting ad fraud operations. By early 2025, it was estimated that Vo1d had infected 1.3 to 1.6 million devices worldwide [2].
From a technical perspective, Vo1d embeds components into system storage to enable itself to download and execute new modules at any time. External researchers further discovered that Vo1d uses Domain Generation Algorithms (DGAs) to create new command-and-control (C2) domains, ensuring that regardless of existing servers being taken down, the malware can quickly reconnect to new ones. Previous published analysis identified dozens of C2 domains and hundreds of DGA seeds, along with new downloader families. Over time, Vo1d has grown increasingly sophisticated with clear signs of stronger obfuscation and encryption methods designed to evade detection [2].
Darktrace’s coverage
Earlier this year, Darktrace observed a surge in Vo1d-related activity across customer environments, with the majority of affected customers based in South Africa. Devices that had been quietly operating as expected began exhibiting unusual network behavior, including excessive DNS lookups. Open-source intelligence (OSINT) has long highlighted South Africa as one of the countries most impacted by Vo1d infections [2].
What makes the recent activity particularly interesting is that the surge observed by Darktrace appears to be concentrated specifically in South African environments. This localized spike suggests that a significant number of devices may have been compromised, potentially due to vulnerable software, outdated firmware, or even preloaded malware. Regions with high prevalence of low-cost, often unpatched devices are especially susceptible, as these everyday consumer electronics can be quietly recruited into the botnet’s network. This specifically appears to be the case with South Africa, where public reporting has documented widespread use of low-cost boxes, such as non-Google-certified Android TV sticks, that frequently ship with outdated firmware [3].
The initial triage highlighted the core mechanism Vo1d uses to remain resilient: its use of DGA. A DGA deterministically creates a large list of pseudo-random domain names on a predictable schedule. This enables the malware to compute hundreds of candidate domains using the same algorithm, instead of using a hard-coded single C2 hostname that defenders could easily block or take down. To ensure reproducible from the infected device’s perspective, Vo1d utilizes DGA seeds. These seeds might be a static string, a numeric value, or a combination of underlying techniques that enable infected devices to generate the same list of candidate domains for a time window, provided the same DGA code, seed, and date are used.
Interestingly, Vo1d’s DGA seeds do not appear to be entirely unpredictable, and the generated domains lack fully random-looking endings. As observed in Figure 1, there is a clear pattern in the names generated. In this case, researchers identified that while the first five characters would change to create the desired list of domain names, the trailing portion remained consistent as part of the seed: 60b33d7929a, which OSINT sources have linked to the Vo1d botnet. [2]. Darktrace’s Threat Research team also identified a potential second DGA seed, with devices in some cases also engaging in activity involving hostnames matching the regular expression /[a-z]{5}fc975904fc9\.(com|top|net). This second seed has not been reported by any OSINT vendors at the time of writing.
Another recurring characteristic observed across multiple cases was the choice of top-level domains (TLDs), which included .com, .net, and .top.
Figure 1: Advanced Search results showing DNS lookups, providing a glimpse on the DGA seed utilized.
The activity was detected by multiple models in Darktrace / NETWORK, which triggered on devices making an unusually large volume of DNS requests for domains uncommon across the network.
During the network investigation, Darktrace analysts traced Vo1d’s infrastructure and uncovered an interesting pattern related to responder ASNs. A significant number of connections pointed to AS16509 (AMAZON-02). By hosting redirectors or C2 nodes inside major cloud environments, Vo1d is able to gain access to highly available and geographically diverse infrastructure. When one node is taken down or reported, operators can quickly enable a new node under a different IP within the same ASN. Another feature of cloud infrastructure that hardens Vo1d’s resilience is the fact that many organizations allow outbound connections to cloud IP ranges by default, assuming they are legitimate. Despite this, Darktrace was able to identify the rarity of these endpoints, identifying the unusualness of the activity.
Analysts further observed that once a generated domain successfully resolved, infected devices consistently began establishing outbound connections to ephemeral port ranges like TCP ports 55520 and 55521. These destination ports are atypical for standard web or DNS traffic. Even though the choice of high-numbered ports appears random, it is likely far from not accidental. Commonly used ports such as port 80 (HTTP) or 443 (HTTPS) are often subject to more scrutiny and deeper inspection or content filtering, making them riskier for attackers. On the other hand, unregistered ports like 55520 and 55521 are less likely to be blocked, providing a more covert channel that blends with outbound TCP traffic. This tactic helps evade firewall rules that focus on common service ports. Regardless, Darktrace was able to identify external connections on uncommon ports to locations that the network does not normally visit.
The continuation of the described activity was identified by Darktrace’s Cyber AI Analyst, which correlated individual events into a broader interconnected incident. It began with the multiple DNS requests for the algorithmically generated domains, followed by repeated connections to rare endpoints later confirmed as attacker-controlled infrastructure. Cyber AI Analyst’s investigation further enabled it to categorize the events as part of the “established foothold” phase of the attack.
Figure 2: Cyber AI Analyst incident illustrating the transition from DNS requests for DGA domains to connections with resolved attacker-controlled infrastructure.
Conclusion
The observations highlighted in this blog highlight the precision and scale of Vo1d’s operations, ranging from its DGA-generated domains to its covert use of high-numbered ports. The surge in affected South African environments illustrate how regions with many low-cost, often unpatched devices can become major hubs for botnet activity. This serves as a reminder that even everyday consumer electronics can play a role in cybercrime, emphasizing the need for vigilance and proactive security measures.
Credit to Christina Kreza (Cyber Analyst & Team Lead) and Eugene Chua (Principal Cyber Analyst & Team Lead)
Edited by Ryan Traill (Analyst Content Lead)
Appendices
Darktrace Model Detections
Anomalous Connection / Devices Beaconing to New Rare IP
Anomalous Connection / Multiple Connections to New External TCP Port
Anomalous Connection / Multiple Failed Connections to Rare Endpoint
Compromise / DGA Beacon
Compromise / Domain Fluxing
Compromise / Fast Beaconing to DGA
Unusual Activity / Unusual External Activity
List of Indicators of Compromise (IoCs)
3.132.75[.]97 – IP address – Likely Vo1d C2 infrastructure
Darktrace Named the Only 2025 Gartner® Peer Insights™ Customers’ Choice for Network Detection and Response
Darktrace: The only Customers’ Choice for NDR in 2025
In a year defined by rapid change across the threat landscape, recognition from those who use and rely on security technology every day means the most.
That’s why we’re proud to share that Darktrace has been named the only Customers’ Choice in the 2025 Gartner® Peer Insights™ Voice of the Customer for Network Detection and Response (NDR).
Out of 11 leading NDR vendors evaluated, Darktrace stood alone as the sole Customers’ Choice, a recognition that we feel reflects not just our innovation, but the trust and satisfaction of the customers who secure their networks with Darktrace every day.
What the Gartner® Peer Insights™ Voice of the Customer means
“Voice of the Customer” is a document that synthesizes Gartner Peer Insights reviews into insights for buyers of technology and services. This aggregated peer perspective, along with the individual detailed reviews, is complementary to Gartner expert research and can play a key role in your buying process. Peers are verified reviewers of a technology product or service, who not only rate the offering, but also provide valuable feedback to consider before making a purchase decision. Vendors placed in the upper-right “Customers’ Choice” quadrant of the “Voice of the Customer” have scores that meet or exceed the market average for both axes (User Interest and Adoption, and Overall Experience).It’s not just a rating. We feel it’s a reflection of genuine customer sentiment and success in the field.
In our view, Customers consistently highlight Darktrace’s ability to:
Detect and respond to unknown threats in real time
Deliver unmatched visibility across IT, OT, and cloud environments
Automate investigations and responses through AI-driven insights
We believe this recognition reinforces what our customers already know: that Darktrace helps them see, understand, and stop attacks others miss.
A rare double: recognized by customers and analysts alike
This distinction follows another major recogniton. Darktrace’s placement as a Leader in the Gartner® Magic Quadrant™ for Network Detection and Response earlier this year.
That makes Darktrace the only vendor to achieve both:
A Leader status in the Gartner Magic Quadrant for NDR, and
A Customers’ Choice in Gartner Peer Insights 2025
It’s a rare double that we feel reflects both industry leadership and customer trust, two perspectives that, together, define what great cybersecurity looks like.
A Customers’ Choice across the network and the inbox
To us, this recognition also builds on Darktrace’s momentum across multiple domains. Earlier this year, Darktrace was also named a Customers’ Choice for Email Security Platforms in the Gartner® Peer Insights™ report.
With more than 1,000 verified reviews across Network Detection and Response, Email Security Platforms, and Cyber Physical Systems (CPS), we at Darktrace are proud to be trusted across the full attack surface, from the inbox to the industrial network.
Thank you to our customers
We’re deeply grateful to every customer who shared their experience with Darktrace on Gartner Peer Insights. Your insights drive our innovation and continue to shape how we protect complex, dynamic environments across the world.
Gartner® Peer Insights™ content consists of the opinions of individual end users based on their own experiences, and should not be construed as statements of fact, nor do they represent the views of Gartner or its affiliates. Gartner does not endorse any vendor, product or service depicted in this content nor makes any warranties, expressed or implied, with respect to this content, about its accuracy or completeness, including any warranties of merchantability or fitness for a particular purpose.
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Gartner, Voice of the Customer for Network Detection and Response, By Peer Community Contributor, 30 October 2025
