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December 16, 2024

Cleo File Transfer Vulnerability: Patch Pitfalls and Darktrace’s Detection of Post-Exploitation Activities

File transfer applications are prime targets for ransomware groups due to their critical role in business operations. Recent vulnerabilities in Cleo's MFT software, namely CVE-2024-50623 and CVE-2024-55956, highlight ongoing risks. Read more about the Darktrace Threat Research team’s investigation into these vulnerabilities.
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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16
Dec 2024

File transfer applications: A target for ransomware

File transfer applications have been a consistent target, particularly for ransomware groups, in recent years because they are key parts of business operations and have trusted access across different parts of an organization that include potentially confidential and personal information about an organization and its employees.

Recent targets of ransomware criminals includes applications like Acellion, Moveit, and GoAnywhere [1]. This seems to have been the case for Cleo’s managed file transfer (MFT) software solutions and the vulnerability CVE-2024-50623.

Threat overview: Understanding Cleo file transfer vulnerability

This vulnerability was believed to have been patched with the release of version 5.8.0.21 in late October 2024. However, open-source intelligence (OSINT) reported that the Clop ransomware group had managed to bypass the initial patch in late November, leading to the successful exploitation of the previously patched CVE.

In the last few days Cleo has published a new vulnerability, CVE-2024-55956, which is not a patch bypass of the CVE-2024-50623 but rather another vulnerability. This is also an unauthenticated file write vulnerability but while CVE-2024-50623 allows for both reading and writing arbitrary files, the CVE-2024-55956 only allows for writing arbitrary files and was addressed in version 5.8.0.24 [2].

Darktrace Threat Research analysts have already started investigating potential signs of devices running the Cleo software with network traffic supporting this initial hypothesis.

Comparison of CVE-2024-50623 and CVE-2024-55956

While CVE-2024-50623 was initially listed as a cross-site scripting issue, it was updated on December 10 to reflect unrestricted file upload and download. This vulnerability could lead to remote code execution (RCE) in versions of Cleo’s Harmony, VLTrader, and LexiCom products prior to 5.8.0.24. Attackers could leverage the fact that files are placed in the "autorun" sub-directory within the installation folder and are immediately read, interpreted, and evaluated by the susceptible software [3].

CVE-2024-55956, refers to an unauthenticated user who can import and execute arbitrary Bash or PowerShell commands on the host system by leveraging the default settings of the Autorun directory [4]. Both CVEs have occurred due to separate issues in the “/Synchronization” endpoint.

Investigating post exploitation patterns of activity on Cleo software

Proof of exploitation

Darktrace’s Threat Research analysts investigated multiple cases where devices identified as likely running Cleo software were detected engaging in unusual behavior. Analysts also attempted to identify any possible association between publicly available indicators of compromise (IoCs) and the exploitation of the vulnerability, using evidence of anomalous network traffic.

One case involved an Internet-facing device likely running Cleo VLTrader software (based on its hostname) reaching out to the 100% rare Lithuanian IP 181.214.147[.]164 · AS 15440 (UAB Baltnetos komunikacijos).

This activity occurred in the early hours of December 8 on the network of a customer in the energy sector. Darktrace detected a Cleo server transferring around over 500 MB of data over multiple SSL connections via port 443 to the Lithuanian IP. External research reported that this IP appears to be a callback IP observed in post-exploitation activity of vulnerable Cleo devices [3].

While this device was regularly observed sending data to external endpoints, this transfer represented a small increase in data sent to public IPs and coupled with the rarity of the destination, triggered a model alert as well as a Cyber AI Analyst Incident summarizing the transfer. Unfortunately, due to the encrypted connection no further analysis of the transmitted data was possible. However, due to the rarity of the activity, Darktrace’s Autonomous Response intervened and prevented any further connections to the IP.

 Model Alert Event Log show repeated connections to the rare IP, filtered with the rarity metric.
Figure 1: Model Alert Event Log show repeated connections to the rare IP, filtered with the rarity metric.
Shows connections to 181.214.147[.]164 and the amount of data transferred.
Figure 2: Shows connections to 181.214.147[.]164 and the amount of data transferred.

On the same day, external connections were observed to the external IP 45.182.189[.]225, along with inbound SSL connections from the same endpoint. OSINT has also linked this IP to the exploitation of Cleo software vulnerabilities [5].

Outgoing connections from a Cleo server to an anomalous endpoint.
Figure 3: Outgoing connections from a Cleo server to an anomalous endpoint.
 Incoming SSL connections from the external IP 45.182.189[.]225.
Figure 4: Incoming SSL connections from the external IP 45.182.189[.]225.

Hours after the last connection to 181.214.147[.]164, the integration detection tool from CrowdStrike, which the customer had integrated with Darktrace, issued an alert. This alert provided additional visibility into host-level processes and highlighted the following command executed on the Cleo server:

“D:\VLTrader\jre\bin\java.exe" -jar cleo.4889

Figure 5: The executed comand “D:\VLTrader\jre\bin\java.exe" -jar cleo.4889 and the Resource Location: \Device\HarddiskVolume3\VLTrader\jre\bin\java.exe.

Three days later, on December 11, another CrowdStrike integration alert was generated, this time following encoded PowerShell command activity on the server. This is consistent with post-exploitation activity where arbitrary PowerShell commands are executed on compromised systems leveraging the default settings of the Autorun directory, as highlighted by Cleo support [6]. According to external researchers , this process initiates connections to an external IP to retrieve JAR files with webshell-like functionality for continued post-exploitation [3]. The IP embedded in both commands observed by Darktrace was 38.180.242[.]122, hosted on ASN 58061(Scalaxy B.V.). There is no OSINT associating this IP with Cleo vulnerability exploitation at the time of writing.

Another device within the same customer network exhibited similar data transfer and command execution activity around the same time, suggesting it had also been compromised through this vulnerability. However, this second device contacted a different external IP, 5.45.74[.]137, hosted on AS 58061 (Scalaxy B.V.).

Like the first device, multiple connections to this IP were detected, with almost 600 MB of data transferred over the SSL protocol.

The Security Integration Detection Model that was triggered  and the PowerShell command observed
Figure 6: The Security Integration Detection Model that was triggered  and the PowerShell command observed
 Incoming connections from the external IP 38.180.242[.]122.
Figure 7: Incoming connections from the external IP 38.180.242[.]122.
Connections to the external IP 5.45.74[.]137.
Figure 8: Connections to the external IP 5.45.74[.]137.
Figure 9: Autonomous Response Actions triggered during the suspicious activities

While investigating potential Cleo servers involved in similar outgoing data activity, Darktrace’s Threat Research team identified two additional instances of likely Cleo vulnerability exploitation used to exfiltrate data outside the network. In those two instances, unusual outgoing data transfers were observed to the IP 176.123.4[.]22 (AS 200019, AlexHost SRL), with around 500 MB of data being exfiltrated over port 443 in one case (the exact volume could not be confirmed in the other instance). This IP was found embedded in encoded PowerShell commands examined by external researchers in the context of Cleo vulnerability exploitation investigations.

Conclusion

Overall, Cleo software represents a critical component of many business operations, being utilized by over 4,000 organizations worldwide. This renders the software an attractive target for threat actors who aim at exploiting internet-facing devices that could be used to compromise the software’s direct users but also other dependent industries resulting in supply chain attacks.

Darktrace / NETWORK was able to capture traffic linked to exploitation of CVE-2024-50623 within models that triggered such as Unusual Activity / Unusual External Data to New Endpoint while its Autonomous Response capability successfully blocked the anomalous connections and exfiltration attempts.

Information on new CVEs, how they're being exploited, and whether they've been patched can be fast-changing, sometimes limited and often confusing. Regardless, Darktrace is able to identify and alert to unusual behavior on these systems, indicating exploitation.

Credit to Maria Geronikolou, Alexandra Sentenac, Emma Fougler, Signe Zaharka and the Darktrace Threat Research team

[related-resource]

Appendices

References

[1] https://blog.httpcs.com/en/file-sharing-and-transfer-software-the-new-target-of-hackers/

[2] https://attackerkb.com/topics/geR0H8dgrE/cve-2024-55956/rapid7-analysis

[3] https://www.huntress.com/blog/threat-advisory-oh-no-cleo-cleo-software-actively-being-exploited-in-the-wild

[4] https://nvd.nist.gov/vuln/detail/CVE-2024-55956

[5] https://arcticwolf.com/resources/blog/cleopatras-shadow-a-mass-exploitation-campaign/

[6] https://support.cleo.com/hc/en-us/articles/28408134019735-Cleo-Product-Security-Advisory-CVE-Pending

[7] https://support.cleo.com/hc/en-us/articles/360034260293-Local-HTTP-Users-Configuration

Darktrace Model Alerts

Anomalous Connection / Data Sent to Rare Domain

Unusual Activity / Unusual External Data to New Endpoint

Unusual Activity / Unusual External Data Transfer

Device / Internet Facing Device with High Priority Alert

Anomalous Server Activity / Rare External from Server

Anomalous Connection / New User Agent to IP Without Hostname

Security Integration / High Severity Integration Incident

Security Integration / Low Severity Integration Detection

Autonomous Response Model Detections

Antigena / Network / Insider Threat / Antigena Large Data Volume Outbound Block

Antigena / Network / Significant Anomaly / Antigena Significant Server Anomaly Block

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

Cyber AI Analyst Incidents

Unusual External Data Transfer

MITRE ATT&CK Mapping

Tactic – Technique

INITIAL ACCESS – Exploit Public-Facing Application

COMMAND AND CONTROL – Application Layer Protocol (Web Protocols)

COMMAND AND CONTROL – Encrypted Channel

PERSISTENCE – Web Shell

EXFILTRATION - Exfiltration Over C2 Channel

IoC List

IoC       Type    Description + Probability

181.214.147[.]164      IP Address       Likely C2 Infrastructure

176.123.4[.]22            IP Address       Likely C2 Infrastructure

5.45.74[.]137               IP Address           Possible C2 Infrastructure

38.180.242[.]122        IP Address       Possible C2 Infrastructure

Get the latest insights on emerging cyber threats

Attackers are adapting, are you ready? This report explores the latest trends shaping the cybersecurity landscape and what defenders need to know.

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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June 9, 2026

Always On, Always Defending: Inside the AI-Driven SOC

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Today’s SOC: A system under pressure

The SOC has been described as the:

  • Control center for security systems management  
  • Operations center for log analysis and alert response
  • Command center for network monitoring and investigation

But the CISO at a manufacturer of industrial power solutions says today’s SOC is far more dynamic:

“The SOC is an active player in a never-ending chess match where the pieces are always moving, the rules are constantly changing, and we’re continuously adjusting our tactical and strategic approaches to keep up.”

This has created a balancing act for cybersecurity professionals:

  • Support expanding digital estates to fuel innovation…or risk limiting business growth
  • Stop advanced cyberattacks at scale…or risk severe financial and reputational impacts

But balancing these responsibilities is increasingly difficult. Attackers are operating at machine speed and scale using sophisticated, adaptive techniques that overwhelm teams and bypass legacy defenses. At the same time, more than half of cybersecurity teams are understaffed, and 65% have unfilled cybersecurity positions (ISACA).

“The SOC is hitting its breaking point,” admits the VP of IT at a U.S.-based risk management services provider.”

“That’s the hard reality,” affirms a Chief Digital and Technology Officer at a North American financial services organization. “SOC teams are drowning in alerts, wasting time researching the most benign incidents while missing critical threats.”

Traditional tools lack the context and autonomous reasoning needed to determine which ones are truly dangerous, requiring analysts to manually review and respond. But with thousands of alerts hitting SOCs daily, the task exceeds human capacity, with recent industry research revealing that 40% to 42% of security alerts now go uninvestigated.

“Our old governance models of throwing bodies at it, that’s not going to work,” says the Group CIO of a multinational holding company. “Attackers move at machine speed, and our defenses have to operate at the same pace. Using AI for cybersecurity is the only way to do that.”

Why AI is essential

AI is about speed, scale, and context.

SOC teams are still expected to find the proverbial “needle in a haystack”, but the haystack keeps growing. As digital infrastructures expand and threat actors use AI to rapidly scale attacks and exploit vulnerabilities, success isn’t about keeping up but changing the approach.

This is where AI comes in, enabling security teams to operate at machine speed and scale by:

  • Analyzing vast amounts of data and correlating signals across domains within seconds
  • Detecting possible threats in real time and taking immediate action to mitigate risk
  • Prioritizing threats by severity and uncovering contextual details for rapid triage

The power of AI isn’t theoretical; it is transforming how today’s businesses operate.

The Chief Digital and Technology Officer at a financial services firm says within a single month of using Darktrace, the solution tracked billions of network events, autonomously investigated tens of millions of those incidents, and added the equivalent of 1,000 analyst hours of investigation. It also found threats that bypassed traditional tools, autonomously responding to contain or disrupt the threat on over 30,000 emails, including 18,000 the firm’s native email filter missed.

When Darktrace says it “takes action on a threat,” it generally means its platform can move beyond just detecting suspicious activity and automatically respond to contain or disrupt the threat—such as isolating a device, slowing or blocking suspicious network traffic, disabling risky user activity, or triggering security workflows—depending on how the system is configured.

AI isn’t about displacing humans.

AI is a powerful tool for handling large-scale data analysis, pattern detection, and repetitive tasks, but it cannot replace human critical thinking. By removing mindless work that does not require judgment, AI frees analysts to focus on what humans do best: applying reasoning, context, and sound decision-making to complex threats.

“AI is a workforce maximizer,” says the Chief Digital and Technology Officer. “It augments our team by monitoring and detecting threats at a scale beyond human capacity while providing the critical context we need to make faster, more confident decisions.

Rather than replacing people, AI is changing how security professionals work. Analysts can reclaim time previously spent on tedious, manual triage to focus on higher priorities and proactive initiatives like advanced threat hunting, strategic risk management, and security enablement and training.

“Aside from risk mitigation, our biggest ROI is in efficiency,” says the Head of Security at global business services provider. “What used to take 90% of our investigation time is now handled automatically, so we can focus on the final 10%, which requires critical thinking."

For SOC teams under pressure, the impact can be transformative, with security leaders reporting significant real-world outcomes using Darktrace Self-Learning AITM, including:

  • Phishing emails reduced by 99%
  • 1 million+ emails autonomously analyzed each month, with no email-based incidents reported
  • Potential threats autonomously neutralized in under four seconds, on average  
  • 99% of investigations conducted autonomously, surfacing only the high-priority 1% of threats for analyst review

How AI optimizes the SOC

To protect the modern enterprise, you absolutely need the right tools,” says CTO at leading European fashion brand. “Without them you’re a victim. With them, you’re a defender. AI and the machine speed detect/response it enables makes it the most critical tool.”

Replacing chaos with clarity and control  

It’s important to note that different AI solutions address different needs. Companies should clearly understand their specific use case and select the solution that best aligns with their goals, requirements, and operational needs.  

When it comes to choosing cybersecurity in a machine-speed threat landscape, time is the most valuable resource. Organizations require AI that can move from insight to action by:

  • Learning an organization’s unique behavioral patterners
  • Correlating signals across domains to detect anomalous activity
  • Prioritizing events and autonomously responding at scale to the vast majority
  • Quarantining high-impact threats until the SOC can investigate
  • Arming analysts with deep, contextual information to accelerate investigations

“Darktrace AI gives us threat detections based on facts, not guesses,” says the Group CIO. “It moves the SOC beyond alert overload to confident, informed decision-making. When Darktrace flags something, we pay attention. False positives are very rare, so we act with speed and confidence without second-guessing.”

Replacing anxiety with confidence and peace of mind

Every missed alert can have real-world consequences.

The strain of maintaining constant vigilance at scale without holistic visibility and automation is taking its toll on security professionals: 66% report increased stress, and nearly half say it’s the reason they’re leaving the field (ISACA).

The CIO at a professional sports organization says that’s not surprising: “If you don’t know what’s going on, anything could be happening. Operating with that level of uncertainty and control is incredibly stressful.”

AI gives SOCs the power to be proactive by unifying telemetry across network, email, identity, and cloud environments to provide a complete picture and a stronger foundation for action. The benefits for analysts, both personally and professionally, are significant:

  • Achieve greater work-life balance: “Knowing that Darktrace has our backs 24/7 and will take immediate action to stop threats  means we can now work normal hours and take vacations without worrying,” says the Chief Digital and Technology Officer.
  • Feel in control with deeper insights: “It not only stops and quarantines threats but also provides the deep context we need to quickly investigate and respond,” explains the Head of Security.  
  • Gain confidence the business is protected 24/7: “We can sleep at night. With Darktrace I’m confident that even with a small team we can protect the business 24/7,” adds the former retail CIO.

The modern SOC: A system of balance

Elevated to a core pillar of business strategy, the modern SOC is now considered:

  • The nerve center of cyber risk and proactive defense
  • The AI-powered command center for operational resilience
  • The strategic hub for contextual decision-making at scale

The SOC has evolved from a reactive center responsible for managing systems into a proactive, frontline defender and strategic business enabler—integral to innovation and growth.

AI is the key to balancing these responsibilities.

“We can only grow as fast as we can secure the business,” says the Head of Security. “AI gives us the speed, scale, and confidence to do both.”

*Metrics are based on the customer’s interview, data and sourced from its monthly Cyber AI Insights reporting.

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June 3, 2026

Stopping Stealth Attacks with Precision: How Núclea Prevented a Breach Without Disruption

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Núclea is a Brazilian data and technology company that supports the country’s financial system by delivering digital services exclusively to banks and financial institutions. Operating in an environment where trust, availability, and data integrity are critical, the company faces a threat landscape that has evolved rapidly—particularly with the rise of AI-driven cyberattacks.

Brazil has experienced a wave of successful cyber incidents targeting financial institutions, many of them enabled by insiders or compromised credentials. The result was a noticeable shift in attacker strategy: instead of focusing on end customers, threat actors began targeting the institutions and platforms that underpin the financial ecosystem itself.

“Attacks became far more directed and contextual,” explains Guilherme, who leads incident response within Núclea’s security platform engineering team. “They weren’t noisy or obviously malicious—they were precise, patient, and designed to blend into normal operations.”

That precision was on full display in January 2026, when Núclea faced one of the most convincing phishing attacks the team had seen.

A real attack, built on trust and context

The attack began with a seemingly routine email.

It was sent from a real Brazilian government institution, using legitimate infrastructure and valid credentials that were later confirmed to have been compromised. Núclea had an established, ongoing relationship with this organization, and the email’s language, tone, and subject matter aligned perfectly with the type of communication the recipient team handled every day.

Attached to the email was a PDF document containing content that looked entirely legitimate.

The problem? A single URL embedded inside that PDF.

“The message itself was correct. The sender was real. The context was familiar. Even the document content made sense,” Guilherme explains. “There was just one small element that didn’t belong.”

That small detail was enough to initiate a full attack chain.

What the attackers were trying to do

If clicked, the URL would have downloaded a malicious payload designed to:

  • Collect information about the user and device
  • Identify where the system was located within the financial ecosystem
  • Install remote access tools to maintain control
  • Deploy an infostealer to extract sensitive data
  • Execute anti-forensic scripts to erase traces of the intrusion

In other words, it was a carefully engineered operation designed for persistence and stealth, not immediate disruption.

The attack also employed urgency—a classic social engineering technique. When the link didn’t open as expected, employees requested assistance from the security team, insisting the document was important and needed to be accessed quickly.

This is precisely the kind of scenario where traditional security tools struggle: almost everything about the interaction is legitimate.

Where Darktrace made the difference

Instead of blocking the entire message or relying on known indicators of compromise, Darktrace focused on behavioral context.

Darktrace recognized:

  • That the sending organization was normally trusted
  • That the communication pattern matched historical behavior
  • That the PDF content itself was not suspicious

But it also identified that the URL embedded within the document deviated from established behavioral patterns.

Rather than disrupting business operations, Darktrace took precise action: it rewrote the URL, preventing the malicious download while leaving the rest of the email untouched.

“When we analyzed it afterward, it became clear how dangerous the attack would have been,” says Guilherme. “But it never progressed—because Darktrace acted at exactly the right point.”

Subsequent forensic analysis confirmed the payload’s malicious intent. The attack never succeeded.

Precision over disruption

For Núclea, this incident reinforced a critical lesson: modern attacks don’t always look malicious—they hide within normal activity.

“What stands out to me is the precision,” Guilherme says. “Darktrace doesn’t rely on big, obvious signals. It’s effective in situations that fall outside the standard patterns we all know.”

Building resilience in a high trust ecosystem

For Núclea, cybersecurity is not just a defensive measure—it’s a business enabler.

Availability failures or successful breaches in the financial ecosystem can have immediate, large-scale consequences, from financial loss to reputational damage. Preventing those outcomes protects not just Núclea, but its partners and customers as well.

“Cyber resilience means keeping the business running—even under attack,” Guilherme explains. “And that requires people, processes, and technology working together.”

As AI continues to accelerate both attacks and defenses, the role of security is evolving. Precision, behavioral understanding, and intelligent automation are no longer optional—they’re essential.

“The easy days were yesterday,” Guilherme says. “The challenges ahead are bigger. We need to be prepared—internally and with partners that help us build resilience.”

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