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February 6, 2025

RansomHub Revisited: New Front-Runner in the Ransomware-as-a-Service Marketplace

Discover how RansomHub is rising in the ransomware landscape, using tools like Atera and Splashtop, reconnaissance tactics, and double extortion techniques.
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.
Written by
Maria Geronikolou
Cyber Analyst
ransomhub revisited ransomware as a serviceDefault blog imageDefault blog imageDefault blog imageDefault blog imageDefault blog imageDefault blog image
06
Feb 2025

In a previous Inside the SOC blog, Darktrace investigated RansomHub and its growing impact on the threat landscape due to its use by the ShadowSyndicate threat group. Here, RansomHub is revisited with new insights on this ransomware-as-a-service (RaaS) platform that has rapidly gained traction among threat actors of late.

In recent months, Darktrace’s Threat Research team has noted a significant uptick in potential compromises affecting the fleet, indicating that RansomHub is becoming a preferred tool for cybercriminals.  This article delves into the increasing adoption of RansomHub, the tactics, techniques, and procedures (TTPs) employed by its affiliates, and the broader implications for organizations striving to protect their systems.

RansomHub overview & background

One notable threat group to have transitioned from ALPHV (BlackCat)-aligned operations to RansomHub-aligned operations is ScatteredSpider [1]. The adoption of RansomHub by ScatteredSpider and other threat actors suggests a possible power shift among threat groups, given the increasing number of cybercriminals adopting it, including those who previously relied on ALPHV’s malware code [2].

ALPHV was a RaaS strain used by cybercriminals to breach Change Healthcare in February 2024 [2]. However, there are claims that the ransom payment never reached the affiliate using ALPHV, leading to a loss of trust in the RaaS. Around the same time, Operation Cronos resulted in the shutdown of LockBit and the abandonment of its affiliates [2]. Consequently, RansomHub emerged as a prominent RaaS successor.

RansomHub targets

The RansomHub ransomware group has been observed targeting various sectors, including critical infrastructure, financial and government services, and the healthcare sector [4]. They use ransomware variants rewritten in GoLang to target both Windows and Linux systems [5]. RansomHub is known for employing double extortion attacks, encrypting data using “Curve25519” encryption [6].

RansomHub tactics and techniques

The attackers leverage phishing attacks and social engineering techniques to lure their victims. Once access is gained, they use sophisticated tools to maintain control over compromised networks and exploit vulnerabilities in systems like Windows, Linux, ESXI, and NAS.

In more recent RansomHub attacks, tools such as Atera and Splashtop have been used to facilitate remote access, while NetScan has been employed to discover and retrieve information about network devices [7].

External researchers have observed that RansomHub uses several legitimate tools, or a tactic known as Living-off-the-Land (LOTL), to carry out their attacks. These tools include:

  • SecretServerSecretStealer: A PowerShell script that allows for the decryption of passwords [1].
  • Ngrok: A legitimate reverse proxy tool that creates a secure tunnel to servers located behind firewalls, used by the group for lateral movement and data exfiltration.
  • Remmina: An open-source remote desktop client for POSIX-based operating systems, enabling threat actors to access remote services [1].

By using these legitimate tools instead of traditional malware, RansomHub can avoid detection and maintain a lower profile during their operations.

Darktrace’s Coverage of RansomHub

Darktrace’s Security Operations Center (SOC) detected several notable cases of likely RansomHub activity across the customer base in recent months. In all instances, threat actors performed network scanning and brute force activities.

During the investigation of a confirmed RansomHub attack in January 2025, the Darktrace Threat Research team identified multiple authentication attempts as attackers tried to retrieve valid credentials. It is plausible that the attackers gained entry to customer environments through their Remote Desktop (RD) web server. Following this, various RDP connections were made to pivot to other devices within the network.

The common element among the cases investigated was that, in most instances, devices were seen performing outgoing connections to splashtop[.]com, a remote access and support software service, after the scanning activity had occurred. On one customer network, following this activity, the same device was seen connecting to the domain agent-api[.]atera[.]com and IP 20.37.139[.]187, which are seemingly linked to Atera, a Remote Monitoring and Management (RMM) tool.

Model Alert Log of an affected device making connections to *atera[.]com.
Figure 1: Model Alert Log of an affected device making connections to *atera[.]com.

In a separate case, a Darktrace observed a device attempting to perform SMB scanning activity, trying to connect to multiple internal devices over port 445. Cyber AI Analyst was able to detect and correlate these individual connections into a single reconnaissance incident.

Similar connections to Remote Monitoring and Management (RMM) tools were also detected in a different customer environment, as alerted by Darktrace’s SOC. Unusual connections to Splashtop and Atera were made from the alerted device. Following this, the same device was observed sending a large volume of data over SSH Rclone to a rare external endpoint on the unusual port 448, triggered multiple models in Darktrace / NETWORK.

Advanced Search graph demonstrating the rarity of the  external IP 38.244.145[.]85  used for data exfiltration.
Figure 2: Advanced Search graph demonstrating the rarity of the  external IP 38.244.145[.]85  used for data exfiltration.
Model Alert Log displaying information related to the suspicious IP, including the port used and its rarity for the network.
Figure 3: Model Alert Log displaying information related to the suspicious IP, including the port used and its rarity for the network.

In the cases observed, data exfiltration occurred alongside the encryption of files likely indicating double extortion tactics. In September 2024, the Darktrace’s Threat Research team identified a 6-digit alphanumeric additional extension similar to “.293ac3”. This case was closely linked to a RansomHub attack, which was also analyzed in a different blog post by Darktrace [8].

Event Log displaying the extension “.293ac3” being appended to encrypted files on an affected customer network.
Figure 4: Event Log displaying the extension “.293ac3” being appended to encrypted files on an affected customer network.

Conclusion

RansomHub exemplifies the evolving RaaS ecosystem, where threat actors capitalize on ready-made platforms to launch sophisticated attacks with ease. The activities observed highlight its growing popularity among cybercriminals. The analysis showed that the different attacks investigated followed a similar pattern of activity.

First, attackers perform reconnaissance activities, including widespread scanning from multiple devices and reverse DNS sweeps. They then use high-privileged credentials to pivot among devices and establish remote connections using RMM tools such as Atera. A common element among most attacks that reached the data encryption stage is the use of a 6-digit alphanumeric extension.

In all cases, Darktrace alerted on the unusual activities observed, creating not only model alerts but also Cyber AI Analyst incidents. Both Darktrace Security Operations Support and Darktrace Managed Threat Detection services provided 24/7 assistance to clients affected by RansomHub. The analyst team continued investigating these incidents, gathering data and IoCs seen in the RansomHub incidents, providing valuable insight and guidance throughout the process.

As RansomHub continues to gain traction, it serves as a stark reminder of the need for robust cybersecurity measures, proactive threat intelligence, and continued vigilance.

Credit to Maria Geronikolou (Cyber Analyst) and Nahisha Nobregas (Senior Cyber Analyst)

[related-resource]

Appendices

Darktrace Model Detections

Network Reconnaissance

o   Device / Network Scan

o   Device / ICMP Address Scan

o   Device / RDP Scan

o   Device / Anomalous LDAP Root Searches

o   Anomalous Connection / SMB Enumeration

o   Device / Spike in LDAP Activity

o   Device / Suspicious Network Scan Activity

Lateral Movement

o   Device / Multiple Lateral Movement Model Alerts

o   Device / Increase in New RPC Services

o   Device / New or Uncommon WMI Activity

o   Device / Possible SMB/NTLM Brute Force

o   Device / SMB Session Brute Force (Non-Admin)

o   Device / Anomalous NTLM Brute Force

o   Compliance / Default Credential Usage

o   Compliance / Outgoing NTLM Request from DC

C2 Activity

o   Anomalous Server Activity / Outgoing from Server

o   Anomalous Connection / Multiple Connections to New External TCP Port

o   Unusual Activity / Unusual External Activity

o   Compliance / Remote Management Tool On Server

Data Exfiltration

o   Unusual Activity / Enhanced Unusual External Data Transfer

o   Anomalous Connection / Outbound SSH to Unusual Port

o   Compliance / SSH to Rare External Destination

o   Unusual Activity / Unusual External Data to New Endpoint

o   Unusual Activity / Unusual External Data Transfer

o   Attack Path Modelling / Unusual Data Transfer on Critical Attack Path

o   Compliance / Possible Unencrypted Password File On Server

Autonomous Response Models

-       Antigena / Network / Significant Anomaly / Antigena Significant Anomaly from Client Block

-       Antigena/Network/Insider Threat/Antigena SMB Enumeration Block

-       Antigena / Network / Significant Anomaly / Antigena Alerts Over Time Block

-       Antigena / Network / Significant Anomaly / Antigena Controlled and Model Alert

List of Indicators of Compromise (IoCs)

o   38.244.145[.]85

o   20.37.139[.]187 agent-api.atera[.]com

o   108.157.150[.]120 ps.atera[.]com

o   st-v3-univ-srs-win-3720[.]api[.]splashtop[.]com

MITRE ATT&CK Mapping

  • RECONNAISSANCE T1592.004
  • RECONNAISSANCE T1595.002
  • DISCOVERY T1046
  • DISCOVERY T1083
  • DISCOVERY T1135
  • DISCOVERY T1018
  • INITIAL ACCESS T1190
  • CREDENTIAL ACCESS T1110
  • LATERAL MOVEMENT T1210
  • COMMAND AND CONTROL T1001
  • EXFILTRATION T1041
  • EXFILTRATION T1567.002

References

[1] https://www.guidepointsecurity.com/blog/worldwide-web-an-analysis-of-tactics-and-techniques-attributed-to-scattered-spider/

[2] https://www.theregister.com/2024/07/16/scattered_spider_ransom/

[3] https://krebsonsecurity.com/2024/03/blackcat-ransomware-group-implodes-after-apparent-22m-ransom-payment-by-change-healthcare/

[4] https://thehackernews.com/2024/09/ransomhub-ransomware-group-targets-210.html

[5] https://www.trendmicro.com/vinfo/us/security/news/ransomware-spotlight/ransomware-spotlight-ransomhub

[6] https://areteir.com/article/malware-spotlight-ransomhub-ransomware/
[7] https://www.security.com/threat-intelligence/ransomhub-knight-ransomware

[8] https://darktrace.com/blog/ransomhub-ransomware-darktraces-investigation-of-the-newest-tool-in-shadowsyndicates-arsenal

Get the latest insights on emerging cyber threats

This report explores the latest trends shaping the cybersecurity landscape and what defenders need to know in 2026

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.
Written by
Maria Geronikolou
Cyber Analyst

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April 24, 2026

Email-Borne Cyber Risk: A Core Challenge for the CISO in the Age of Volume and Sophistication

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The challenge for CISOs

Despite continuous advances in security technologies, humans continue to be exploited by attackers. Credential abuse and social actions like phishing are major factors, accounting for around 60% of all breaches. These attacks rely less on technical vulnerabilities and more on exploiting human behavior and organizational processes. 

From my perspective as a former CISO, protecting humans concentrates three of today’s most pressing challenges: the sheer volume of email-based threats, their increasing sophistication, and the limitations of traditional employee awareness programs in moving the needle on risk. 

My personal experience of security awareness training as a CISO

With over 20 years’ experience as an ICT and Cybersecurity leader across various international organizations, I’ve seen security awareness training (SAT) in many guises. And while the cyber landscape is evolving in every direction, the effectiveness of SAT is reaching a plateau.  

Most programs I’ve seen follow a familiar pattern. Training is delivered through a combination of eLearning modules and internal sessions designed to reinforce IT policies. Employees are typically required to complete a slide deck or video, followed by a multiple-choice quiz. Occasional phishing simulations are distributed throughout the year.

The content is often static and unpersonalized, based on known threats that may already be outdated. Every employee regardless of role or risk exposure receives the same training and the same simulated phishing templates, from front-desk staff to the CEO.

The problem with traditional SAT programs

The issue with the approach to SAT outlined above is that the distribution of power is imbalanced. Humans will always be fallible, particularly when faced with increasingly sophisticated attacks. Providing generic, low-context training risks creating false confidence rather than genuine resilience. Let’s look at some of the problems in detail.

Timing and delivery

Employees today operate under constant cognitive load, making lots of rapid decisions every day to reduce their email volumes. Yet if employees are completing training annually, or on an ad hoc basis, it becomes a standalone occurrence rather than a continuous habit.  

As a result, retention is low. Employees often forget the lessons within weeks, a phenomenon known as the ‘Ebbinghaus Forgetting Curve.’

The graph illustrates that when you first learn something, the information disappears at an exponential rate without retention. In fact, according to the curve, you forget 50% of all new information within a day, and 90% of all new information within a week.  

Simultaneously, most training is conducted within a separate interface. Because it takes place away from the actual moment of decision-making, the "teachable moment" is lost. There is a cognitive disconnect between the action (clicking a link in Outlook) and the education (watching a video in a browser). 

People

In the context of professional risk management, the risks faced by different users are different. Static learning such as everyone receiving the same ‘Password Reset’ email doesn’t help users prepare for the specific threats they are likely to face. It also contributes to user fatigue, driven by repetitive training. And if users receive tests at the same time, news spreads among colleagues, hurting the efficacy of the test.  

Staff turnover introduces further risk. In many organizations, new employees gain access to systems before receiving meaningful training, reducing onboarding to little more than policy acknowledgment.

Measuring success

In my experience, solutions are standalone, without any correlation to other tools in the security stack. In some cases, the programs are delivered by HR rather than the security team, creating a complete silo.  

As a result, SAT is often perceived as a compliance exercise rather than a capability building function. The result is that poor-quality training does little to reduce the likelihood of compromise, regardless of completion rates or quiz performance.

What a modern SAT solution should look like

For today’s CISO, email represents the convergence point of high-volume, high-impact, and human-centric threats. Despite significant security investments, it remains one of the most difficult channels to secure effectively. Given these constraints, CISOs must evolve their approach to SAT.

Success lies in a balanced strategy one that combines advanced technology, attack surface reduction, and pragmatic user enablement, without over-relying on human vigilance as the final line of defense.

This means moving beyond traditional SAT toward continuous, contextual awareness, realistic simulations, and tight integration with security outcomes.

Three requirements for a modern SAT solution

  • Invisible protection: The optimum security solution is one that assists users without impeding their experience. The objective is to enhance human capabilities, rather than simply delivering a lecture. 
  • Real-time feedback: Rather than a monthly quiz, the ideal system would provide a prompt or warning when a user is about to engage with something suspicious. 
  • Positive culture: Shifting the focus away from a "gotcha" culture, which is a contributing factor to a resentment, and instead empowers employees to serve as "sensors" for the company. 

Discover how personalized security coaching can strengthen your human layer and make your email defenses more resilient. Explore Darktrace / Adaptive Human Defense.

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About the author
Karim Benslimane
VP, Field CISO

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April 21, 2026

How a Compromised eScan Update Enabled Multi‑Stage Malware and Blockchain C2

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The rise of supply chain attacks

In recent years, the abuse of trusted software has become increasingly common, with supply chain compromises emerging as one of the fastest growing vectors for cyber intrusions. As highlighted in Darktrace’s Annual Threat Report 2026, attackers and state-actors continue to find significant value in gaining access to networks through compromised trusted links, third-party tools, or legitimate software. In January 2026, a supply chain compromise affecting MicroWorld Technologies’ eScan antivirus product was reported, with malicious updates distributed to customers through the legitimate update infrastructure. This, in turn, resulted in a multi‑stage loader malware being deployed on compromised devices [1][2].

An overview of eScan exploitation

According to eScan’s official threat advisory, unauthorized access to a regional update server resulted in an “incorrect file placed in the update distribution path” [3]. Customers associated with the affected update servers who downloaded the update during a two-hour window on January 20 were impacted, with affected Windows devices subsequently have experiencing various errors related to update functions and notifications [3].

While eScan did not specify which regional update servers were affected by the malicious update, all impacted Darktrace customer environments were located in the Europe, Middle East, and Africa (EMEA) region.

External research reported that a malicious 32-bit executable file , “Reload.exe”, was first installed on affected devices, which then dropped the 64-bit downloader, “CONSCTLX.exe”. This downloader establishes persistence by creating scheduled tasks such as “CorelDefrag”, which are responsible for executing PowerShell scripts. Subsequently, it evades detection by tampering with the Windows HOSTS file and eScan registry to prevent future remote updates intended for remediation. Additional payloads are then downloaded from its command-and-control (C2) server [1].

Darktrace’s coverage of eScan exploitation

Initial Access and Blockchain as multi-distributed C2 Infrastructure

On January 20, the same day as the aforementioned two‑hour exploit window, Darktrace observed multiple devices across affected networks downloading .dlz package files from eScan update servers, followed by connections to an anomalous endpoint, vhs.delrosal[.]net, which belongs to the attackers’ C2 infrastructure.

The endpoint contained a self‑signed SSL certificate with the string “O=Internet Widgits Pty Ltd, ST=SomeState, C=AU”, a default placeholder commonly used in SSL/TLS certificates for testing and development environments, as well as in malicious C2 infrastructure [4].

Utilizing a multi‑distributed C2 infrastructure, the attackers also leveraged domains linked with the Solana open‑source blockchain for C2 purposes, namely “.sol”. These domains were human‑readable names that act as aliases for cryptocurrency wallet addresses. As browsers do not natively resolve .sol domains, the Solana Naming System (formerly known as Bonfida, an independent contributor within the Solana ecosystem) provides a proxy service, through endpoints such as sol-domain[.]org, to enable browser access.

Darktrace observed devices connecting to blackice.sol-domain[.]org, indicating that attackers were likely using this proxy to reach a .sol domain for C2 activity. Given this behavior, it is likely that the attackers leveraged .sol domains as a dead drop resolver, a C2 technique in which threat actors host information on a public and legitimate service, such as a blockchain. Additional proxy resolver endpoints, such as sns-resolver.bonfida.workers[.]dev, were also observed.

Solana transactions are transparent, allowing all activity to be viewed publicly. When Darktrace analysts examined the transactions associated with blackice[.]sol, they observed that the earliest records dated November 7, 2025, which coincides with the creation date of the known C2 endpoint vhs[.]delrosal[.]net as shown in WHOIS Lookup information [4][5].

WHOIS Look records of the C2 endpoint vhs[.]delrosal[.]net.
Figure 1: WHOIS Look records of the C2 endpoint vhs[.]delrosal[.]net.
 Earliest observed transaction record for blackice[.]sol on public ledgers.
Figure 2: Earliest observed transaction record for blackice[.]sol on public ledgers.

Subsequent instructions found within the transactions contained strings such as “CNAME= vhs[.]delrosal[.]net”, indicating attempts to direct the device toward the malicious endpoint. A more recent transaction recorded on January 28 included strings such as “hxxps://96.9.125[.]243/i;code=302”, suggesting an effort to change C2 endpoints. Darktrace observed multiple alerts triggered for these endpoints across affected devices.

Similar blockchain‑related endpoints, such as “tumama.hns[.]to”, were also observed in C2 activities. The hns[.]to service allows web browsers to access websites registered on Handshake, a decentralized blockchain‑based framework designed to replace centralized authorities and domain registries for top‑level domains. This shift toward decentralized, blockchain‑based infrastructure likely reflects increased efforts by attackers to evade detection.

In outgoing connections to these malicious endpoints across affected networks, Darktrace / NETWORK recognized that the activity was 100% rare and anomalous for both the devices and the wider networks, likely indicative of malicious beaconing, regardless of the underlying trusted infrastructure. In addition to generating multiple model alerts to capture this malicious activity across affected networks, Darktrace’s Cyber AI Analyst was able to compile these separate events into broader incidents that summarized the entire attack chain, allowing customers’ security teams to investigate and remediate more efficiently. Moreover, in customer environments where Darktrace’s Autonomous Response capability was enabled, Darktrace took swift action to contain the attack by blocking beaconing connections to the malicious endpoints, even when those endpoints were associated with seemingly trustworthy services.

Conclusion

Attacks targeting trusted relationships continue to be a popular strategy among threat actors. Activities linked to trusted or widely deployed software are often unintentionally whitelisted by existing security solutions and gateways. Darktrace observed multiple devices becoming impacted within a very short period, likely because tools such as antivirus software are typically mass‑deployed across numerous endpoints. As a result, a single compromised delivery mechanism can greatly expand the attack surface.

Attackers are also becoming increasingly creative in developing resilient C2 infrastructure and exploiting legitimate services to evade detection. Defenders are therefore encouraged to closely monitor anomalous connections and file downloads. Darktrace’s ability to detect unusual activity amidst ever‑changing tactics and indicators of compromise (IoCs) helps organizations maintain a proactive and resilient defense posture against emerging threats.

Credit to Joanna Ng (Associate Principal Cybersecurity Analyst) and Min Kim (Associate Principal Cybersecurity Analyst) and Tara Gould (Malware Researcher Lead)

Edited by Ryan Traill (Content Manager)

Appendices

Darktrace Model Detections

  • Anomalous File::Zip or Gzip from Rare External Location
  • Anomalous Connection / Suspicious Self-Signed SSL
  • Anomalous Connection / Rare External SSL Self-Signed
  • Anomalous Connection / Suspicious Expired SSL
  • Anomalous Server Activity / Anomalous External Activity from Critical Network Device

List of Indicators of Compromise (IoCs)

  • vhs[.]delrosal[.]net – C2 server
  • tumama[.]hns[.]to – C2 server
  • blackice.sol-domain[.]org – C2 server
  • 96.9.125[.]243 – C2 Server

MITRE ATT&CK Mapping

  • T1071.001 - Command and Control: Web Protocols
  • T1588.001 - Resource Development
  • T1102.001 - Web Service: Dead Drop Resolver
  • T1195 – Supple Chain Compromise

References

[1] https://www.morphisec.com/blog/critical-escan-threat-bulletin/

[2] https://www.bleepingcomputer.com/news/security/escan-confirms-update-server-breached-to-push-malicious-update/

[3] hxxps://download1.mwti.net/documents/Advisory/eScan_Security_Advisory_2026[.]pdf

[4] https://www.virustotal.com/gui/domain/delrosal.net

[5] hxxps://explorer.solana[.]com/address/2wFAbYHNw4ewBHBJzmDgDhCXYoFjJnpbdmeWjZvevaVv

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About the author
Joanna Ng
Associate Principal Analyst
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