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
Max Heinemeyer
Global Field CISO
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17
Mar 2021
On March 11 and 12, 2021, Darktrace detected multiple attempts by a broad campaign to attack vulnerable servers in customer environments. The campaign targeted Internet-facing Microsoft Exchange servers, exploiting the recently discovered ProxyLogon vulnerability (CVE-2021-26855).
While this exploit was initially attributed to a group known as Hafnium, Microsoft has announced that the vulnerability is also being rapidly weaponized by other threat actors. These new, unattributed campaigns, which have never been seen before, have been disrupted by Cyber AI in real time.
Hafnium copycats
As soon as a vulnerability is made public it is common for there to be an influx of attacks as hackers capitalize on the chaos and attempt to compromise vulnerable networks.
Patches are rapidly reverse-engineered by hackers once they have been published by the vendor, leading to mass high-impact exploits. At the same time, the offensive tooling trickles down from the first adopters, such as nation-state actors, to ransomware gangs and other opportunistic attackers. Darktrace has observed this exact phenomenon as a result of Hafnium’s attacks against vulnerable Microsoft Exchange email servers this month.
Exchange servers attacked: AI analysis
Cyber AI has observed threat actors attempting to download and install malware using ProxyLogon as the initial attack vector. For customers with Autonomous Response, the malicious payload was intercepted at this point, stopping the attack before any developments.
In other Darktrace customer environments, the Darktrace Immune System identified and alerted on every stage of the attack. Generally, the malware has been observed acting as a generic backdoor, without much follow-up activity. Various forms of command and control (C2) channels were detected, including Telegra[.]ph. In a few intrusions, the attackers installed cryptocurrency miners.
Once a foothold has been established in the digital environment, it is likely that the actors will begin a hands-on-keyboard attack, exfiltrating data, moving laterally, or deploying ransomware.
Figure 1: Timeline of a typical ProxyLogon exploit
After the ProxyLogon vulnerability was exploited, the Exchange servers reached out to the malicious domain microsoftsoftwaredownload[.]com, utilizing a PowerShell User Agent. Darktrace flagged this anomalous behavior as the particular User Agent had never been used before by the Exchange server, let alone to access a malicious domain which had never been observed in the network.
Figure 2: Darktrace revealing an anomalous PowerShell connection
The malware executable was masqueraded as a ZIP file, further trying to obfuscate the attack. Darktrace identified this highly anomalous file download and the masqueraded file.
Figure 3: Darktrace revealing key information around the anomalous file download
In some cases, Darktrace AI also observed cryptocurrency mining seconds or minutes after the initial malware download.
Figure 4: Darktrace’s Crypto Currency Mining model is breached
In terms of C2 traffic, Darktrace has observed various potential channels. Around the time of the malware download, some of the Exchange servers began to beacon out to several external destinations using unusual SSL or TLS encrypted connections.
Telegra[.]ph — popular messenger application
dev.opendrive[.]com — cloud storage service
od[.]lk — cloud storage service
In this case, Darktrace recognized that none of these three external domains had ever been contacted before by anybody in the organization, let alone in a beaconing fashion. The fact that these communications started around the same time as the malware downloads strongly suggests a correlation. Darktrace’s Cyber AI Analyst automatically began an investigation into the incident, stitching together these events into one coherent narrative.
Investigating with AI
Cyber AI Analyst then automatically created a summary incident report about the activity, covering the malware download as well as the various C2 channels observed.
Figure 5: Cyber AI Analyst automatically generating a high-level incident summary
Looking at an infected Exchange server ([REDACTED].local) from a birds-eye perspective shows that Darktrace created various alerts when the attack hit. Every one of the colored dots in the graph below represents a major anomaly detected by Darktrace.
Figure 6: Darktrace reveals the anomalous number of connections and subsequent model breaches
This activity was prioritized as the most urgent incident in Cyber AI Analyst among a full week’s worth of data. In this particular organization, there were only four incidents for that week in total in Cyber AI Analyst. Such precise and clear alerting allows security teams to immediately understand the top threats facing their digital environment, without being overwhelmed by unnecessary alerts and false positives.
Machine-speed response
For customers with Darktrace Antigena, Antigena autonomously acted to block all outgoing traffic to malicious external endpoints on the relevant ports. This behavior is held for several hours to interrupt the threat actor from escalating the attack, while giving security teams time to react and remediate.
Antigena responded within seconds of the attack starting, effectively containing the attack in its earliest stage – without interrupting regular business activity (emails could still be sent and received), and despite this being a zero-day campaign.
This is not the first time Darktrace has stopped an attack leveraging a zero-day or a freshly released n-day vulnerability. Back in March 2020, Darktrace detected APT41 exploiting the Zoho ManageEngine vulnerability, two weeks before public attribution.
It is highly likely that there will be more cyber-criminals exploiting ProxyLogon in the wake of Hafnium. And while the recent Exchange server vulnerabilities were today’s threat, next time it might be a software or hardware supply chain attack, or a different zero-day. Novel threats are emerging every week. In this climate we now find ourselves in, where ‘known unknowns’ which are difficult or impossible to pre-define are the new norm, we need to be more adaptable and proactive than ever.
As soon as an attacker begins to exhibit unusual activity, Darktrace AI will detect it, even if there is no threat intelligence associated with the attack. This is where Darktrace works best, autonomously detecting, investigating and responding to advanced and never-before-seen threats in real time.
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.
Hola VPN Abuse: From Proxy Traffic to Malware and Cryptomining
Introduction
In enterprise environments, non-compliant software traffic can introduce unexpected exposure by creating unmanaged paths for outbound connectivity. Hola VPN is a notable example because of its peer-to-peer design, which can effectively turn user devices into routing or exit nodes for other parties’ traffic, shifting the risk profile from that of a traditional virtual private network (VPN) to something closer to a distributed proxy.
As a result, the appearance of Hola-related activity, whether from prior installation or unintended background connections, should be treated with caution. Such activity may provide a foothold for malicious behavior, including lateral movement or command-and-control communication.
This blog explores how Hola-associated activity appeared as part of broader patterns of suspicious behavior observed across the Darktrace customer base.
The campaign
In February and March 2026, Darktrace observed similar anomalous activity across multiple customer environments, with affected devices showing consistent behavioral patterns. These included connections to multiple *.hola[.]org endpoints using Hola-related user agents, suggesting interaction with Hola infrastructure rather than isolated or incidental traffic.
Following these connections, affected customer environments showed downloads of suspicious executable files from rare external endpoints 188.241.219[.]55 and 184.241.218[.]111. Both endpoints have been flagged as potentially malicious by open-source intelligence (OSINT) [1][2].
These downloads were conducted using consistent user agents across impacted customers, specifically ‘Hola svc_js_win32/1.249.408’ and ‘Hola svc_js_win32/1.251.389’, suggesting a possible association with Hola-related activity.
Notably, this pattern aligns with recent reporting that, in some cases, Hola distributed an undeclared executable component, me[.]exe, which was later assessed to be a likely Monero-mining binary introduced via a compromised delivery pipeline [3].
Case Study 1
Darktrace first observed a new device on January 19, 2026, within a customer environment based in the Europe, Middle East, and Africa (EMEA) region. On the same day it appeared on the network, the device communicated with multiple pieces of Hola VPN-linked infrastructure before downloading a binary from a hola[.]org subdomain.
Figure 1: Cyber AI Analyst investigation highlighting Hola VPN service activity potentially associated with subsequent HTTP command-and-control (C2) connections.
Subsequent Darktrace telemetry revealed a recurring pattern of activity from the day the device was first observed through to March 4, 2026. During this period, the device repeatedly issued HTTP GET requests to the URI /bwfile?size=1048576, each returning a 200 OK response, indicating successful file retrieval.
This behavior was accompanied by a POST request to /bwfile, followed by an additional GET request for a significantly larger file at /bwfile?size=26214400, suggesting a deliberate and structured file transfer pattern.
Notably, the binary download activity was not tied to a single static host. Instead, it was observed across multiple URLs that changed over time while remaining within the same hola[.]org domain. This pattern suggests the use of rotating or distributed delivery infrastructure rather than a fixed endpoint.
Figure 2: Variation in URLs over time within the same hola[.]org domain, indicating the use of dynamically changing endpoints.
Across these events, the activity was consistently associated with the user agent Hola svc_js_win32/1.249.408, further linking the traffic to Hola-related service components. Amid these persistent and unusual connections, on February 22, Darktrace observed the device connecting to 188.241.219[.]55/proxy-peer-windows-amd64[.]exe, resulting in the download of an executable file.
Figure 3: File transfer event showing the download of an executable from the rare external endpoint 188.241.219[.]55.
Based on its file hash, the downloaded file was assessed as a likely Trojan downloader [4], with import hash (imphash) values showing similarities to samples linked to Vidar, Rhadamanthys, and Stealc according to OSINT [5]. Overall, this sequence of activity suggests that Hola-related connectivity may have been leveraged as part of a broader malware delivery chain.
Darktrace’s Autonomous Response
Due to the highly unusual activity observed, Darktrace Autonomous Response was triggered by the device’s behavior. However, as the customer deployment was configured in “Human Confirmation” mode, manual approval was required before any action could be taken.
Had the deployment been set to “Fully Autonomous” mode, Darktrace would have automatically:
Blocked connections to the associated ports and external endpoints
Prevented all outgoing network connections from the device
Enforced the device’s established ‘pattern of life’, allowing normal activity to continue while restricting any anomalous behavior
Figure 4: Example of a Darktrace Autonomous Response model highlighting the action that would have been taken, demonstrating how the system identifies anomalous behavior and applies targeted containment measures to restrict suspicious network activity.
Case Study 2
While the first case focused on anomalous activity from a newly observed device, Darktrace also identified cases in which devices had already been communicating with Hola-related endpoints prior to the suspected campaign. This may suggest pre-existing Hola usage within the environment, potentially increasing exposure and creating an avenue for subsequent suspicious activity.
One case involved three devices within a customer network based in the Americas (AMS). In this instance, a different payload was identified: me[.]exe, a potentially malicious cryptocurrency miner also referred to as HolaMonitorService[.]exe [6][7]. The downloads were observed from infrastructure similar to that seen in Case 1, including an IP address within the same 188.241.0.0/16 subnet.
Connections to *.hola[.]org, alongside the use of potential Hola-related user agents consistent with those in Case 1, were also identified, further suggesting a link between the observed activity and Hola-associated infrastructure.
Darktrace observed activity indicative of unusual VPN usage on the first affected device on February 2, followed by telemetry suggesting potential Tor usage. This was later followed by the download of me[.]exe on March 10 from 188.241.218[.]111. Notably, this device was the earliest among the three within the deployment to exhibit the presence of the suspicious executable.
Figure 5: Cyber AI Analyst detection highlighting the download of a suspicious executable from a similar external endpoint in a separate deployment.
On March 5, 2026, the second affected device exhibited a slightly different progression, initiating connections to http-test1[.]hola[.]org using the user agent ‘hola_get’. This activity was followed by the download of me[.]exe from the same endpoint on March 13, consistent with the broader pattern of Hola-related downloads observed across the environment.
Figure 6: Example of Hola VPN-related connectivity observed on the network prior to the suspected campaign, indicating pre-existing usage that may have contributed to subsequent activity.
The final affected device within this customer’s network demonstrated a more limited but related pattern, also downloading me[.]exe on March 17 using the same ‘hola_get’ user agent.
While the earlier Hola VPN usage observed across the deployment may not have been directly related to the suspected malware campaign, it may nonetheless have contributed to reduced visibility. The presence of pre-existing Hola-related traffic could have obscured malicious activity, making it more difficult to distinguish legitimate usage from attacker-driven behavior and, in turn, hindering the timely identification of the emerging compromise.
Darktrace’s Autonomous Response
For this deployment, the customer had their Autonomous Response capability configured in “Fully Autonomous” mode, allowing Darktrace to take action without human intervention. As a result, the system was able to autonomously disrupt the activity as soon as relevant events were identified through model detections.
Figure 7: Darktrace Autonomous Response actions taken against suspicious activity linked to Hola VPN.
Suspected cryptomining activity
As previously noted, some of the observed executable payloads appear to be linked to cryptomining malware. Across a subset of affected customer environments, this assessment was further supported by subsequent device activity consistent with Monero mining. Affected devices established follow-on connections to multiple external endpoints aligned with known mining infrastructure, indicating post-download execution.
Considering the broader sequence of activity, this pattern may point to a wider form of abuse in which legitimate VPN-related traffic is used to mask or facilitate malicious behavior following compromise.
On several devices, the download of executable files, including a newly observed peer[.]exe, was followed by alerts indicative of cryptocurrency mining activity. Mining-related credentials such as ‘x’ were observed using the Minergate protocol to communicate with endpoints within the 89.125.255.0/24 subnet and 188.241.218[.]111, the same endpoint involved in earlier download activity. Additional credentials appeared to reflect device-specific CPU identifiers, for example ‘12th Gen Intel(R) Core (TM) i5-1235U’.
Observed mining methods included login, submit, and job, consistent with active participation in a pool-based mining workflow rather than passive or incidental contact. The login method indicates that the host authenticated to the mining service as a worker, job reflects the assignment of computational tasks, and submit shows completed work being returned to the pool [8]. This sequence suggests that affected devices were actively contributing processing resources as part of an unauthorized distributed mining operation.
The presence of unauthorized cryptominers can lead to degraded system performance and reduced device stability. Beyond the immediate resource impact, such activity often serves as an indicator of a broader compromise rather than an isolated issue. This may increase the risk of further malware deployment, persistence mechanisms, and lateral movement, particularly in environments where the initial intrusion has not been fully contained.
Conclusion
Across affected environments, detections such as unusual VPN usage, connections to Hola infrastructure, anomalous HTTP activity, suspicious file downloads, and subsequent cryptomining behavior were linked into a single, evolving incident narrative. This aggregation provided a clearer view of attack progression, enabling security teams to understand not just isolated alerts, but the full sequence of compromise from initial contact through to post-exploitation.
Ultimately, these activities show that the risk posed by non-compliant software such as Hola VPN can extend far beyond simple policy violations. What began as traffic to Hola-related infrastructure was, in multiple cases, followed by behavior suggesting deliberate misuse, including suspicious executable downloads using Hola-related user agents and, in some instances, evidence of active cryptomining. These were not isolated anomalies, but elements of a broader pattern in which seemingly benign proxy or VPN-related communications may have created a pathway for malicious delivery and unauthorized resource exploitation.
The significance of this activity lies not only in the downloads or mining, but in what it reveals about an attacker’s ability to blend malicious operations into traffic associated with software that may already have a foothold in the environment. When unapproved software operates within an enterprise, it can reduce visibility, blur the distinction between legitimate and malicious traffic, and create opportunities to extend compromise in ways that are persistent and difficult to detect. Darktrace’s anomaly-based approach enables these behavioral distinctions to be identified, regardless of whether the device is new or long established within the network.
Credit to Min Kim (Associate Principal Analyst), Priya Thapa (Senior Cyber Analyst) Edited by Ryan Traill (Content Manager)
![Variation in URLs over time within the same hola[.]org domain, indicating the use of dynamically changing endpoints.](https://cdn.prod.website-files.com/626ff4d25aca2edf4325ff97/6a304bdeff111215c0436931_Screenshot%202026-06-15%20at%2012.00.43%E2%80%AFPM.png)
![File transfer event showing the download of an executable from the rare external endpoint 188.241.219[.]55.](https://cdn.prod.website-files.com/626ff4d25aca2edf4325ff97/6a304c2468d20aeff16a2721_Screenshot%202026-06-15%20at%2012.01.53%E2%80%AFPM.png)
