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October 30, 2024

Post-Exploitation Activities on Fortinet Devices: A Network-Based Analysis

This blog explores recent findings from Darktrace's Threat Research team on active exploitation campaigns targeting Fortinet appliances. This analysis focuses on the September 2024 exploitation of FortiManager via CVE-2024-47575, alongside related malicious activity observed in June 2024.
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
Adam Potter
Senior Cyber Analyst
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30
Oct 2024

Introduction: Uncovering active exploitation of Fortinet vulnerabilities

As part of the Darktrace Threat Research team's routine analysis of October's Patch Tuesday vulnerabilities, the team began searching for signs of active exploitation of a critical vulnerability (CVE-2024-23113) affecting the FortiGate to FortiManager (FGFM) protocol.[1]

Although the investigation was prompted by an update regarding CVE 2024-23113, results of the inquiry yielded evidence of widespread exploitation of Fortinet devices in both June and September 2024 potentially via multiple vulnerabilities including CVE 2024-47575. Analysts identified two clusters of activity involving overlapping indicators of compromise (IoCs), likely constituting unique campaigns targeting Fortinet appliances.

This blog will first highlight the finding and analysis of the network-based indicators of FortiManager post-exploitation activity in September, likely involving CVE 2024-47575. The article will then briefly detail a similar pattern of malicious activity observed in June 2024 that involved similar IoCs that potentially comprises a distinct campaign targeting Fortinet perimeter devices.

Fortinet CVE Disclosures

FortiManager devices allow network administrators to manage Fortinet devices on organizations’ networks.[2] One such subset of devices managed through this method are Fortinet firewalls known as FortiGate. These manager and firewall devices communicate with each other via a custom protocol known as FortiGate to FortiManager (FGFM), whereby devices can perform reachability tests and configuration-related actions and reporting.[3] By default, FortiManager devices operate this protocol via port 541.[4]

Fortinet Product Security Incident Response Team released multiple announcements revealing vulnerabilities within the daemon responsible for implementing operability of the FGFM service. Specifically, CVE 2024-23113 enables attackers to potentially perform arbitrary remote command execution through the use of a specially crafted format string to a FortiGate device running the “fgfm daemon”.[5][6]  Similarly, the exploitation of CVE 2024-47575  could also allow remote command execution due to a missing authentication mechanism when targeting specifically FortiManager devices.[7][8]  Given how prolific both FortiGate and FortiManager devices are within the global IT security ecosystem, Darktrace analysts hypothesized that there may have been specific targeting of such devices within the customer base using these vulnerabilities throughout mid to late 2024.

Campaign Analysis

In light of these vulnerability disclosures, Darktrace’s Threat Research team began searching for signs of active exploitation by investigating file download, lateral movement or tooling activity from devices that had previously received suspicious connections on port 541. The team first noticed increases in suspicious activity involving Fortinet devices particularly in mid-September 2024. Further analysis revealed a similar series of activities involving some overlapping devices identified in June 2024. Analysis of these activity clusters revealed a pattern of malicious activity against likely FortiManager devices, including initial exploitation, payload retrieval, and exfiltration of probable configuration data.

Below is an overview of malicious activity we have observed by sector and region:

Sector and region affected by malicious activity on fortigate devices
The sectors of affected customers listed above are categorized according to the United Kingdom’s Standard Industrial Classification (SIC).

Initial Exploitation of FortiManager Devices

Across many of the observed cases in September, activity began with the initial exploitation of FortiManager devices via incoming connectivity over TLS/SSL. Such activity was detected due to the rarity of the receiving devices accepting connections from external sources, particularly over destination port 541. Within nearly all investigated incidents, connectivity began with the source IP, 45.32.41[.]202, establishing an SSL session with likely FortiManager devices.  Device types were determined through a combination of the devices’ hostnames and the noted TLS certificate issuer for such encrypted connections.

Due to the encrypted nature of the connection, it was not possible to ascertain the exploit used in the analyzed cases. However, given the similarity of activities targeting FortiManager devices and research conducted by outside firms, attackers likely utilized CVE 2024-47575.[9] For example, the source IP initiating the SSL sessions also has been referenced by Mandiant as engaging in CVE 2024-47575 exploitation. In addition to a consistent source IP for the connections, a similar JA3 hash was noted across multiple examined accounts, suggesting a similarity in source process for the activity.

In most cases observed by Darktrace, the incoming connectivity was followed by an outgoing connection on port 443 to the IP 45.32.41[.]202. Uncommon reception of encrypted connections over port 541, followed by the initiation of outgoing SSL connections to the same endpoint would suggest probable successful exploitation of FortiManager CVEs during this time.

Model alert logs highlighting the incoming connectivity over port 541 to the FortiManager devices followed by outgoing connection to the external IP.
Figure 1: Model alert logs highlighting the incoming connectivity over port 541 to the FortiManager devices followed by outgoing connection to the external IP.

Payload Retrieval

Investigated devices commonly retrieved some form of additional content after incoming connectivity over port 541. Darktrace’s Threat Research team noted how affected devices would make HTTP GET requests to the initial exploitation IP for the URI: /dom.js. This URI, suggestive of JavaScript content retrieval, was then validated by the HTTP response content type. Although Darktrace could see the HTTP content of the connections, usage of destination port 443 featured prominently during these HTTP requests, suggesting an attempt at encryption of the session payload details.

Figure 2: Advanced Search HTTP log to the exploitation IP noting the retrieval of JavaScript content using the curl user agent.

Cyber AI Analyst investigation into the initial exploitation activity. This incident emphasizes the rare external connectivity over port 443 requesting JavaScript content following the incoming connections over port 541.
Figure 3: Cyber AI Analyst investigation into the initial exploitation activity. This incident emphasizes the rare external connectivity over port 443 requesting JavaScript content following the incoming connections over port 541.

The operators of the campaign also appear to have used a consistent user agent for payload retrieval: curl 8.4.0. Usage of an earlier version of the curl (version 7 .86.0) was only observed in one instance. The incorporation of curl utility to establish HTTP connections therefore suggests interaction with command-line utilities on the inspected Fortinet hosts. Command-line interaction also adds validity to the usage of exploits such as CVE 2024-47575 which enable unauthenticated remote command execution. Moreover, given the egress of data seen by the devices receiving this JavaScript content, Darktrace analysts concluded that this payload likely resulted in the configuration aggregation activity noted by external researchers.

Data Exfiltration

Nearly all devices investigated during the September time period performed some form of data exfiltration using the HTTP protocol. Most frequently, devices would initiate these HTTP requests using the same curl user agent already observed during web callback activity.  Again, usage of this tool heavily suggests interaction with the command-line interface and therefore command execution.

The affected device typically made an HTTP POST request to one or both of the following two rare external IPs: 104.238.141[.]143 and 158.247.199[.]37. One of the noted IPs, 104.238.141[.]143, features prominently within external research conducted by Mandiant during this time. These HTTP POST requests nearly always sent data to the /file endpoint on the destination IPs. Analyzed connections frequently noted an HTTP mime type suggestive of compressed archive content. Some investigations also revealed specific filenames for the data sent externally: “.tm”. HTTP POST requests occurred without a specified hostname. This would suggest the IP address may have already been cached locally on the device from a running process or the IP address was hardcoded into the details of unwarranted code running on the system. Moreover, many such POSTs occurred without a GET request, which can indicate exfiltration activity.

Model alert logs noting both the connection to the IP 158.247.199[.]37 over port 443 without a hostname, and the unusual activity metric describing how the request was made without a prior HTTP GET request. Such activity can indicate malicious data exfiltration.
Figure 4: Model alert logs noting both the connection to the IP 158.247.199[.]37 over port 443 without a hostname, and the unusual activity metric describing how the request was made without a prior HTTP GET request. Such activity can indicate malicious data exfiltration.

Interestingly, in many investigations, analysts noticed a lag period between the initial access and exploitation, and the exfiltration of data via HTTP. Such a pause, sometimes over several hours to over a day, could reflect the time needed to aggregate data locally on the host or as a strategic pause in activity to avoid detection. While not present within every compromise activity logs inspected, the delay could represent slight adjustments in behavior during the campaign by the threat actor.

Figure 5: Advanced search logs showing both the payload retrieval and exfiltration activity, emphasizing the gap in time between payload retrieval and exfiltration via HTTP POST request.

HTTP and file identification details identified during this time also directly correspond to research conducted by Mandiant. Not only do we see overlap in IPs identified as receiving the posted data (104.238.141[.]143) we also directly observed an overlap in filenames for the locally aggregated configuration data. Moreover, the gzip mime type identified in multiple customer investigations also corresponds directly to exfiltration activity noted by Mandiant researchers.

Advanced search logs noting the filename and URL of the posted data to one of the exfiltration IPs. The .tm filename corresponds to the locally stored file on affected FortiManager devices analyzed by external researchers.
Figure 6: Advanced search logs noting the filename and URL of the posted data to one of the exfiltration IPs. The .tm filename corresponds to the locally stored file on affected FortiManager devices analyzed by external researchers.

Activity detected in June 2024

Common indicators

Analysts identified a similar pattern of activity between June 23 and June 25. Activity in this period involved incoming connections from the aforementioned IP 45.32.41[.]202 on either port 541 or port 443 followed by an outgoing connection to the source. This behavior was then followed by HTTP POSTs to the previously mentioned IP address 158.247.199[.]37 in addition to the novel IP: 195.85.114[.]78  using same URI ‘/file’ noted above. Given the commonalties in indicators, time period, and observed behaviors, this grouping of exploitation attempts appears to align closely with the campaign described by Mandiant and may represent exploitation of CVE 2024-47575 in June 2024. The customers targeted in June fall into the same regions and sectors as seen those in the September campaign.

Deviations in behavior

Notably, Darktrace detected a different set of actions during the same June timeframe despite featuring the same infrastructure. This activity involved an initial incoming connection from 158.247.199[.]37 to an internal device on either port 541 or port 443. This was then followed by an outgoing HTTP connection to 158.247.199[.]37 on port 443 with a URI containing varying external IPs. Upon further review, analysts noticed the IPs listed may be the public IPs of the targeted victim, suggesting a potential form device registration by the threat actor or exploit validation. While the time period and infrastructure closely align with the previous campaign described, the difference in activity may suggest another threat actor sharing infrastructure or the same threat actor carrying out a different campaign at the same time. Although the IP 45.32.41[.]202 was contacted, paralleling activity seen in September, analysts did notice a different payload received from the external host, a shell script with the filename ver.sh.

Figure 7: AI Analyst timeline noting the suspicious HTTP behavior from a FortiManager device involving the IP 158.247.199[.] 37.

Darktrace's depth of detection and investigation

Darktrace detected spikes in anomalous behavior from Fortinet devices within the customer base between September 22 and 23, 2024. Following an in-depth investigation into affected accounts and hosts, Darktrace identified a clear pattern where one, or multiple, threat actors leveraged CVEs affecting likely FortiManager devices to execute commands on the host, retrieve malicious content, and exfiltrate sensitive data. During this investigation, analysts then identified possibly related activity in June 2024 highlighted above.

The gathering and exfiltration of configuration data from network security management or other perimeter hosts is a technique that can enable future access by threat actors. This parallels activity previously discussed by Darktrace focused on externally facing devices, such as Palo Alto Networks firewall devices.  Malicious entities could utilize stolen configuration data and potentially stored passwords/hashes to gain initial access in the future, irrespective of the state of device patching. This data can also be potentially sold by initial access brokers on illicit sites. Moreover, groups can leverage this information to establish persistence mechanisms within devices and host networks to enable more impactful compromise activity.

Uncover threat pattens before they strike your network

Network and endpoint management services are essential tools for network administrators and will remain a critical part of IT infrastructure. However, these devices are often configured as internet-facing systems, which can unintentionally expose organizations networks' to attacks. Internet exposure provides malicious groups with novel entry routes into target environments. Although threat actors can swap vulnerabilities to access target networks, the exploitation process leaves behind unusual traffic patterns, making their presence detectable with the right network detection tools.

By detecting the unusual patterns of network traffic which inevitably ensue from exploitation of novel vulnerabilities, Darktrace’s anomaly-based detection and response approach can continue to identify and inhibit such intrusion activities irrespective of exploit used. Eulogizing the principle of least privilege, configuration and asset management, and maintaining the CIA Triad across security operations will continue to help security teams boost their defense posture.

See how anomaly-based detection can enhance your security operations—schedule a personalized demo today.

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Credit to Adam Potter (Senior Cyber Analyst), Emma Foulger (Principal Cyber Analyst), Nahisha Nobregas (Senior Cyber Analyst), Hyeongyung Yeom (Principal Cyber Analyst & Analyst Team Lead, East Asia), Sam Lister (Senior Cyber Analyst)

Appendix

Model Alerts

  • Anomalous Connection / Posting HTTP to IP without Hostname
  • Anomalous Connection / Callback on Web Facing Device
  • Anomalous Server Activity / New Internet Facing Server
  • Anomalous Server Activity / Outgoing from Server

Cyber AI Analyst Incidents

  • Possible HTTP Command and Control
  • Possible HTTP Command and Control to Multiple Endpoints

IoCs

Indicator – Type - Description

104.238.141[.]143 -  IP Address  - C2 infrastructure

158.247.199[.]37 - IP Address - C2 infrastructure

45.32.41[.]202 - IP Address - C2 infrastructure

104.238.141[.]143/file – URL - C2 infrastructure

158.247.199[.]37/file  - URL - C2 infrastructure

45.32.41[.]202/dom.js – URL - C2 infrastructure

.tm – Filename - Gzip file

MITRE Attack Framework

  • Initial Access
    T1190 Exploiting Public-Facing Application
  • Execution:
    T1059 Command and Scripting Interpreter  (Sub-Techniques: T1059.004 Unix Shell, T1059.008 Network Device CLI)
  • Discovery:
    T1083 File and System Discovery
    T1057 Process Discovery
  • Collection:
    T1005 Data From Local System
  • Command and Control:
    T1071 Application Layer Protocols (Sub-Technique:
    T1071.001 Web Protocols)
    T1573  Encrypted Channel
    T1573.001  Symmetric Cryptography
    T1571 Non-Standard Port
    T1105 Ingress Tool Transfer
    T1572 Protocol Tunnelling 
  • Exfiltration:
    T1048.003 Exfiltration Over Unencrypted Non-C2 Protocol

References

{1} https://cloud.google.com/blog/topics/threat-intelligence/fortimanager-zero-day-exploitation-cve-2024-47575/

{2} https://docs.fortinet.com/document/fortimanager/6.4.0/ports-and-protocols/606094/fortigate-fortimanager-protocol#:~:text=The%20FortiGate%2DFortiManager%20(FGFM),by%20using%20the%20FGFM%20protocol.

{3)https://docs.fortinet.com/document/fortigate/6.4.0/ports-and-protocols/373486/fgfm-fortigate-to-fortimanager-protocol
{4} https://www.fortiguard.com/psirt/FG-IR-24-029
{5} https://www.fortiguard.com/psirt/FG-IR-24-423
{6}https://www.fortinet.com/content/dam/fortinet/assets/data-sheets/fortimanager.pdf

{7} https://doublepulsar.com/burning-zero-days-fortijump-fortimanager-vulnerability-used-by-nation-state-in-espionage-via-msps-c79abec59773

{8} https://darktrace.com/blog/post-exploitation-activities-on-pan-os-devices-a-network-based-analysis

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
Adam Potter
Senior Cyber Analyst

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September 15, 2025

SEO Poisoning and Fake PuTTY sites: Darktrace’s Investigation into the Oyster backdoor

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What is SEO poisoning?

Search Engine Optimization (SEO) is the legitimate marketing technique of improving the visibility of websites in organic search engine results. Businesses, publishers, and organizations use SEO to ensure their content is easily discoverable by users. Techniques may include optimizing keywords, creating backlinks, or even ensuring mobile compatibility.

SEO poisoning occurs when attackers use these same techniques for malicious purposes. Instead of improving the visibility of legitimate content, threat actors use SEO to push harmful or deceptive websites to the top of search results. This method exploits the common assumption that top-ranking results are trustworthy, leading users to click on URLs without carefully inspecting them.

As part of SEO poisoning, the attacker will first register a typo-squatted domain, slightly misspelled or otherwise deceptive versions of real software sites, such as putty[.]run or puttyy[.]org. These sites are optimized for SEO and often even backed by malicious Google ads, increasing the visibility when users search for download links. To achieve that, threat actors may embed pages with strategically chosen, high-value keywords or replicate content from reputable sources to elevate the domain’s perceived authority in search engine algorithms [4]. In more advanced operations, these tactics are reinforced with paid promotion, such as Google ads, enabling malicious domains to appear above organic search results as sponsored links. This placement not only accelerates visibility but also impacts an unwarranted sense of legitimacy to unsuspected users.

Once a user lands on one of these fake pages, they are presented with what looks like a legitimate software download option. Upon clicking the download indicator, the user will be redirected to another separate domain that actually hosts the payload. This hosting domain is usually unrelated to the nominally referenced software. These third-party sites can involve recently registered domains but may also include legitimate websites that have been recently compromised. By hosting malware on a variety of infrastructure, attackers can prolong the availability of distribution methods for these malicious files before they are taken down.

What is the Oyster backdoor?

Oyster, also known as Broomstick or CleanUpLoader, is a C++ based backdoor malware first identified in July 2023. It enables remote access to infected systems, offering features such as command-line interaction and file transfers.

Oyster has been widely adopted by various threat actors, often as an entry point for ransomware attacks. Notable examples include Vanilla Tempest and Rhysida ransomware groups, both of which have been observed leveraging the Oyster backdoor to enhance their attack capabilities. Vanilla Tempest is known for using Oyster’s stealth persistence to maintain long-term access within targeted networks, often aligning their operations with ransomware deployment [5]. Rhysida has taken this further by deploying Oyster as an initial access tool in ransomware campaigns, using it to conduct reconnaissance and move laterally before executing encryption activities [6].

Once installed, the backdoor gathers basic system information before communicating with a command-and-control (C2) server. The malware largely relies on a ‘cmd.exe’ instance to execute commands and launch other files [1].

In previous SEO poisoning cases, the file downloaded from the fake pages is not just PuTTY, but a trojanized version that includes the stealthy Oyster backdoor. PuTTY is a free and open-source terminal emulator for Windows that allows users to connect to remote servers and devices using protocols like SSH and Telnet. In the recent campaign, once a user visits the fake software download site, ranked highly through SEO poisoning, the malicious payload is downloaded through direct user interaction and subsequently installed on the local device, initiating the compromise. The malware then performs two actions simultaneously: it installs a fully functional version of PuTTY to avoid user suspicion, while silently deploying the Oyster backdoor. Given PuTTY’s nature, it is prominently used by IT administrators with highly privileged account as opposed to standard users in a business, possibly narrowing the scope of the targets.

Oyster’s persistence mechanism involves creating a Windows Scheduled Task that runs every few minutes. Notably, the infection uses Dynamic Link Library (DLL) side loading, where a malicious DLL, often named ‘twain_96.dll’, is executed via the legitimate Windows utility ‘rundll32.exe’, which is commonly used to run DLLs [2]. This technique is frequently used by malicious actors to blend their activity with normal system operations.

Darktrace’s Coverage of the Oyster Backdoor

In June 2025, security analysts at Darktrace identified a campaign leveraging search engine manipulation to deliver malware masquerading as the popular SSH client, PuTTY. Darktrace / NETWORK’s anomaly-based detection identified signs of malicious activity, and when properly configured, its Autonomous Response capability swiftly shut down the threar before it could escalate into a more disruptive attack. Subsequent analysis by Darktrace’s Threat Research team revealed that the payload was a variant of the Oyster backdoor.

The first indicators of an emerging Oyster SEO campaign typically appeared when user devices navigated to a typosquatted domain, such as putty[.]run or putty app[.]naymin[.]com, via a TLS/SSL connection.

Figure 1: Darktrace’s detection of a device connecting to the typosquatted domain putty[.]run.

The device would then initiate a connection to a secondary domain that hosts the malicious installer, likely triggered by user interaction with redirect elements on the landing page. This secondary site may not have any immediate connection to PuTTY itself but is instead a hijacked blog, a file-sharing service, or a legitimate-looking content delivery subdomain.

Figure 2: Darktrace’s detection of the device making subsequent connections to the payload domain.

Following installation, multiple affected devices were observed attempting outbound connectivity to rare external IP addresses, specifically requesting the ‘/secure’ endpoint as noted within the declared URIs. After the initial callback, the malware continued communicating with additional infrastructure, maintaining its foothold and likely waiting for tasking instructions. Communication patterns included:

·       Endpoints with URIs /api/kcehc and /api/jgfnsfnuefcnegfnehjbfncejfh

·       Endpoints with URI /reg and user agent “WordPressAgent”, “FingerPrint” or “FingerPrintpersistent”

This tactic has been consistently linked to the Oyster backdoor, which has shown similar URI patterns across multiple campaigns [3].

Darktrace analysts also noted the sophisticated use of spoofed user agent strings across multiple investigated customer networks. These headers, which are typically used to identify the application making an HTTP request, are carefully crafted to appear benign or mimic legitimate software. One common example seen in the campaign is the user agent string “WordPressAgent”. While this string references a legitimate web application or plugin, it does not appear to correspond to any known WordPress services or APIs. Its inclusion is most likely designed to mimic background web traffic commonly associated with WordPress-based content management systems.

Figure 3: Cyber AI Analyst investigation linking the HTTP C2 activity.

Case-Specific Observations

While the previous section focused on tactics and techniques common across observed Oyster infections, a closer examination reveals notable variations and unique elements in specific cases. These distinct features offer valuable insights into the diverse operational approaches employed by threat actors. These distinct features, from unusual user agent strings to atypical network behavior, offer valuable insights into the diverse operational approaches employed by the threat actors. Crucially, the divergence in post-exploitation activity reflects a broader trend in the use of widely available malware families like Oyster as flexible entry points, rather than fixed tools with a single purpose. This modular use of the backdoor reflects the growing Malware-as-a-Service (MaaS) ecosystem, where a single initial infection can be repurposed depending on the operator’s goals.

From Infection to Data Egress

In one observed incident, Darktrace observed an infected device downloading a ZIP file named ‘host[.]zip’ via curl from the URI path /333/host[.]zip, following the standard payload delivery chain. This file likely contained additional tools or payloads intended to expand the attacker’s capabilities within the compromised environment. Shortly afterwards, the device exhibited indicators of probable data exfiltration, with outbound HTTP POST requests featuring the URI pattern: /upload?dir=NAME_FOLDER/KEY_KEY_KEY/redacted/c/users/public.

This format suggests the malware was actively engaged in local host data staging and attempting to transmit files from the target machine. The affected device, identified as a laptop, aligns with the expected target profile in SEO poisoning scenarios, where unsuspecting end users download and execute trojanized software.

Irregular RDP Activity and Scanning Behavior

Several instances within the campaign revealed anomalous or unexpected Remote Desktop Protocol (RDP) sessions occurring shortly after DNS requests to fake PuTTY domains. Unusual RDP connections frequently followed communication with Oyster backdoor C2 servers. Additionally, Darktrace detected patterns of RDP scanning, suggesting the attackers were actively probing for accessible systems within the network. This behavior indicates a move beyond initial compromise toward lateral movement and privilege escalation, common objectives once persistence is established.

The presence of unauthorized and administrative RDP sessions following Oyster infections aligns with the malware’s historical role as a gateway for broader impact. In previous campaigns, Oyster has often been leveraged to enable credential theft, lateral movement, and ultimately ransomware deployment. The observed RDP activity in this case suggests a similar progression, where the backdoor is not the final objective but rather a means to expand access and establish control over the target environment.

Cryptic User Agent Strings?

In multiple investigated cases, the user agent string identified in these connections featured formatting that appeared nonsensical or cryptic. One such string containing seemingly random Chinese-language characters translated into an unusual phrase: “Weihe river is where the water and river flow.” Legitimate software would not typically use such wording, suggesting that the string was intended as a symbolic marker rather than a technical necessity. Whether meant as a calling card or deliberately crafted to frame attribution, its presence highlights how subtle linguistic cues can complicate analysis.

Figure 4: Darktrace’s detection of malicious connections using a user agent with randomized Chinese-language formatting.

Strategic Implications

What makes this campaign particularly noteworthy is not simply the use of Oyster, but its delivery mechanism. SEO poisoning has traditionally been associated with cybercriminal operations focused on opportunistic gains, such as credential theft and fraud. Its strength lies in casting a wide net, luring unsuspecting users searching for popular software and tricking them into downloading malicious binaries. Unlike other campaigns, SEO poisoning is inherently indiscriminate, given that the attacker cannot control exactly who lands on their poisoned search results. However, in this case, the use of PuTTY as the luring mechanism possibly indicates a narrowed scope - targeting IT administrators and accounts with high privileges due to the nature of PuTTY’s functionalities.

This raises important implications when considered alongside Oyster. As a backdoor often linked to ransomware operations and persistent access frameworks, Oyster is far more valuable as an entry point into corporate or government networks than small-scale cybercrime. The presence of this malware in an SEO-driven delivery chain suggests a potential convergence between traditional cybercriminal delivery tactics and objectives often associated with more sophisticated attackers. If actors with state-sponsored or strategic objectives are indeed experimenting with SEO poisoning, it could signal a broadening of their targeting approaches. This trend aligns with the growing prominence of MaaS and the role of initial access brokers in today’s cybercrime ecosystem.

Whether the operators seek financial extortion through ransomware or longer-term espionage campaigns, the use of such techniques blurs the traditional distinctions. What looks like a mass-market infection vector might, in practice, be seeding footholds for high-value strategic intrusions.

Credit to Christina Kreza (Cyber Analyst) and Adam Potter (Senior Cyber Analyst)

Appendices

MITRE ATT&CK Mapping

·       T1071.001 – Command and Control – Web Protocols

·       T1008 – Command and Control – Fallback Channels

·       T0885 – Command and Control – Commonly Used Port

·       T1571 – Command and Control – Non-Standard Port

·       T1176 – Persistence – Browser Extensions

·       T1189 – Initial Access – Drive-by Compromise

·       T1566.002 – Initial Access – Spearphishing Link

·       T1574.001 – Persistence – DLL

Indicators of Compromise (IoCs)

·       85.239.52[.]99 – IP address

·       194.213.18[.]89/reg – IP address / URI

·       185.28.119[.]113/secure – IP address / URI

·       185.196.8[.]217 – IP address

·       185.208.158[.]119 – IP address

·       putty[.]run – Endpoint

·       putty-app[.]naymin[.]com – Endpoint

·       /api/jgfnsfnuefcnegfnehjbfncejfh

·       /api/kcehc

Darktrace Model Detections

·       Anomalous Connection / New User Agent to IP Without Hostname

·       Anomalous Connection / Posting HTTP to IP Without Hostname

·       Compromise / HTTP Beaconing to Rare Destination

·       Compromise / Large Number of Suspicious Failed Connections

·       Compromise / Beaconing Activity to External Rare

·       Compromise / Quick and Regular Windows HTTP Beaconing

·       Device / Large Number of Model Alerts

·       Device / Initial Attack Chain Activity

·       Device / Suspicious Domain

·       Device / New User Agent

·       Antigena / Network / Significant Anomaly / Antigena Breaches Over Time Block

·       Antigena / Network / External Threat / Antigena Suspicious Activity Block

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

References

[1] https://malpedia.caad.fkie.fraunhofer.de/details/win.broomstick

[2] https://arcticwolf.com/resources/blog/malvertising-campaign-delivers-oyster-broomstick-backdoor-via-seo-poisoning-trojanized-tools/

[3] https://hunt.io/blog/oysters-trail-resurgence-infrastructure-ransomware-cybercrime

[4] https://www.crowdstrike.com/en-us/cybersecurity-101/social-engineering/seo-poisoning/

[5] https://blackpointcyber.com/blog/vanilla-tempest-oyster-backdoor-netsupport-unknown-infostealers-soc-incidents-blackpoint-apg/

[6] https://areteir.com/article/rhysida-using-oyster-backdoor-in-attacks/

The content provided in this blog is published by Darktrace for general informational purposes only and reflects our understanding of cybersecurity topics, trends, incidents, and developments at the time of publication. While we strive to ensure accuracy and relevance, the information is provided “as is” without any representations or warranties, express or implied. Darktrace makes no guarantees regarding the completeness, accuracy, reliability, or timeliness of any information presented and expressly disclaims all warranties.

Nothing in this blog constitutes legal, technical, or professional advice, and readers should consult qualified professionals before acting on any information contained herein. Any references to third-party organizations, technologies, threat actors, or incidents are for informational purposes only and do not imply affiliation, endorsement, or recommendation.

Darktrace, its affiliates, employees, or agents shall not be held liable for any loss, damage, or harm arising from the use of or reliance on the information in this blog.

The cybersecurity landscape evolves rapidly, and blog content may become outdated or superseded. We reserve the right to update, modify, or remove any content without notice.

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About the author
Christina Kreza
Cyber Analyst

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September 9, 2025

The benefits of bringing together network and email security

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In many organizations, network and email security operate in isolation. Each solution is tasked with defending its respective environment, even though both are facing the same advanced, multi-domain threats.  

This siloed approach overlooks a critical reality: email remains the most common vector for initiating cyber-attacks, while the network is the primary stage on which those attacks progress. Without direct integration between these two domains, organizations risk leaving blind spots that adversaries can exploit.  

A modern security strategy needs to unify email and network defenses, not just in name, but in how they share intelligence, conduct investigations, and coordinate response actions. Let’s take a look at how this joined-up approach delivers measurable technical, operational, and commercial benefits.

Technical advantages

Pre-alert intelligence: Gathering data before the threat strikes

Most security tools start working when something goes wrong – an unusual login, a flagged attachment, a confirmed compromise. But by then, attackers may already be a step ahead.

By unifying network and email security under a single AI platform (like the Darktrace Active AI Security Platform), you can analyze patterns across both environments in real time, even when there are no alerts. This ongoing monitoring builds a behavioral understanding of every user, device, and domain in your ecosystem.

That means when an email arrives from a suspicious domain, the system already knows whether that domain has appeared on your network before – and whether its behavior has been unusual. Likewise, when new network activity involves a domain first spotted in an email, it’s instantly placed in the right context.

This intelligence isn’t built on signatures or after-the-fact compromise indicators – it’s built on live behavioral baselines, giving your defenses the ability to flag threats before damage is done.

Alert-related intelligence: Connecting the dots in real time

Once an alert does fire, speed and context matter. The Darktrace Cyber AI Analyst can automatically investigate across both environments, piecing together network and email evidence into a single, cohesive incident.

Instead of leaving analysts to sift through fragmented logs, the AI links events like a phishing email to suspicious lateral movement on the recipient’s device, keeping the full attack chain intact. Investigations that might take hours – or even days – can be completed in minutes, with far fewer false positives to wade through.

This is more than a time-saver. It ensures defenders maintain visibility after the first sign of compromise, following the attacker as they pivot into network infrastructure, cloud services, or other targets. That cross-environment continuity is impossible to achieve with disconnected point solutions or siloed workflows.

Operational advantages

Streamlining SecOps across teams

In many organizations, email security is managed by IT, while network defense belongs to the SOC. The result? Critical information is scattered between tools and teams, creating blind spots just when you need clarity.

When email and network data flow into a single platform, everyone is working from the same source of truth. SOC analysts gain immediate visibility into email threats without opening another console or sending a request to another department. The IT team benefits from the SOC’s deeper investigative context.

The outcome is more than convenience: it’s faster, more informed decision-making across the board.

Reducing time-to-meaning and enabling faster response

A unified platform removes the need to manually correlate alerts between tools, reducing time-to-meaning for every incident. Built-in AI correlation instantly ties together related events, guiding analysts toward coordinated responses with higher confidence.

Instead of relying on manual SIEM rules or pre-built SOAR playbooks, the platform connects the dots in real time, and can even trigger autonomous response actions across both environments simultaneously. This ensures attacks are stopped before they can escalate, regardless of where they begin.

Commercial advantages

While purchasing “best-of-breed" for all your different tools might sound appealing, it often leads to a patchwork of solutions with overlapping costs and gaps in coverage. However good a “best-in-breed" email security solution might be in the email realm, it won't be truly effective without visibility across domains and an AI analyst piecing intelligence together. That’s why we think “best-in-suite" is the only “best-in-breed" approach that works – choosing a high-quality platform ensures that every new capability strengthens the whole system.  

On top of that, security budgets are under constant pressure. Managing separate vendors for email and network defense means juggling multiple contracts, negotiating different SLAs, and stitching together different support models.

With a single provider for both, procurement and vendor management become far simpler. You deal with one account team, one support channel, and one unified strategy for both environments. If you choose to layer on managed services, you get consistent expertise across your whole security footprint.

Even more importantly, an integrated AI platform sets the stage for growth. Once email and network are under the same roof, adding coverage for other attack surfaces – like cloud or identity – is straightforward. You’re building on the same architecture, not bolting on new point solutions that create more complexity.

Check out the white paper, The Modern Security Stack: Why Your NDR and Email Security Solutions Need to Work Together, to explore these benefits in more depth, with real-world examples and practical steps for unifying your defenses.

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About the author
Mikey Anderson
Product Marketing Manager, Network Detection & Response
Your data. Our AI.
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