Detecting Metamorphic Malware with Darktrace's AI Technology
Detect metamorphic malware with Darktrace's AI. Learn how it uncovers self-modifying cyber-attacks and stops threats that evade traditional security measures.
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
Justin Fier
SVP, Red Team Operations
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30
Jul 2017
Some of the most insidious threats that Darktrace finds use self-modifying technology to hide their presence on the network. These attacks can dynamically change their threat signatures, automatically extract data, and spread without a human controller.
Recently, we discovered anomalous activity on the network of a major US university. After investigation, we found that the anomaly was the ‘Smoke Malware Loader’ which employs numerous techniques to evade internal security. Most notably, the malware generates fake traffic to hide its presence.
Darktrace observed the initial infection when three anomalous executables were transferred over plain text. The malware did not match any known threat signatures, allowing it to bypass the network’s perimeter controls.
C1ulyq1wLrMBs6LG00 on Thu Sep 8, 13:19:01 Co2eAJ2GifEkWut700 on Thu Sep 8, 12:09:52 CdcZeu200UOsuf5u00 on Wed Sep 14, 16:38:44
The connections originated from a suspicious external domain that the company had never communicated with before:
lago666[.]com (91.243.193.149)
Both the anomalous download and the beaconing activity represented major deviations from the unique ‘pattern of life’ learned by the Enterprise Immune System.
Although the payload circumvented the network’s perimeter security, the company also had an alternate security system monitoring network flow. This tool raised an alert when the download occurred, but it was deemed a ‘false positive’ because the malware proceeded to install new, previously unknown versions of the executable to the Windows registry.
After the self-modifying modules were uploaded to the company device, a large number of HTTP POST requests were sent against /smk/log.php to the following domains:
The malware attempted to transfer data to these external destinations, but to hide its tracks, the remote machine replied with a fake 404 error code. These connections were deemed highly anomalous by Darktrace’s AI algorithms.
Since the payload was designed to be compatible with the password grabber module2 – which is often deployed side-by-side with Smoke Malware Loader – the data attempting to leave the network likely contained user credentials and passwords.
In conjunction with the initial transfer, another anomalous file was then delivered to a different device. This activity indicated that the threat actor was likely attempting to move laterally across the network:
hxxp://cdn.che[.]moe/izgmcx.exe (connection UID: CGH6uV3G5tdKSNY800) to 10.1.105.117 on Mon Sep 12 at 08:02:03.
Darktrace detected each anomaly in real time as the situation developed. By using AI algorithms to continuously learn normal behavior, Darktrace was able to monitor the malware’s changing threat signature.
Traditional security tools – no matter how advanced – are incapable of detecting such sophisticated threats. Legacy controls rely on rules and signatures, and these threats are specifically designed to bypass rules and signatures.
Darktrace’s real-time threat detection allowed the university’s security team to quarantine the infected devices before the malware could burrow deeper into the network, and before the attacker could use the passwords to further compromise the network. Darktrace then assisted the security team as they remediated the situation and changed their security protocols and passwords.
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.
ダークトレースのアナリストは、韓国のユーザーを標的とした、北朝鮮（DPRK）が関係していると思われる攻撃を検知しました。このキャンペーンはJavascriptEncoded（JSE）スクリプトと政府機関を装ったおとり文書を使ってVisual Studio Code（VS Code）トンネルを展開し、リモートアクセスを確立していました。
技術分析
図1: 「2026年上半期国立大学院夜間プログラムの学生選抜に関する文書」という表題のおとり文書。
このキャンペーンで確認されたサンプルは、Hangul Word Processor （HWPX） 文書に偽装したJSEファイルであり、スピアフィッシングEメールを使って標的に送付されたと考えられます。このJSEファイルは複数のBase64エンコードされたブロブを含み、Windows Script Hostによって実行されます。このHWPXファイルは“2026年上半期国立大学院夜間プログラムの学生選抜に関する文書(1)”という名前で、C:\ProgramDataにあり、おとりとして開かれます。この文書は韓国の公務員に関連する事務を管掌する政府機関、人事革新処を装ったものでした。文書内のメタデータから、脅威アクターは文書を本物らしくみせるため、政府ウェブサイトから文書を取得し、編集したと思われます。
React2Shell Reflections: Cloud Insights, Finance Sector Impacts, and How Threat Actors Moved So Quickly
Introduction
Last month’s disclosure of CVE 2025-55812, known as React2Shell, provided a reminder of how quickly modern threat actors can operationalize newly disclosed vulnerabilities, particularly in cloud-hosted environments.
The vulnerability was discovered on December 3, 2025, with a patch made available on the same day. Within 30 hours of the patch, a publicly available proof-of-concept emerged that could be used to exploit any vulnerable server. This short timeline meant many systems remained unpatched when attackers began actively exploiting the vulnerability.
Darktrace researchers rapidly deployed a new honeypot to monitor exploitation of CVE 2025-55812 in the wild.
Within two minutes of deployment, Darktrace observed opportunistic attackers exploiting this unauthenticated remote code execution flaw in React Server Components, leveraging a single crafted request to gain control of exposed Next.js servers. Exploitation quickly progressed from reconnaissance to scripted payload delivery, HTTP beaconing, and cryptomining, underscoring how automation and pre‑positioned infrastructure by threat actors now compress the window between disclosure and active exploitation to mere hours.
For cloud‑native organizations, particularly those in the financial sector, where Darktrace observed the greatest impact, React2Shell highlights the growing disconnect between patch availability and attacker timelines, increasing the likelihood that even short delays in remediation can result in real‑world compromise.
Cloud insights
In contrast to traditional enterprise networks built around layered controls, cloud architectures are often intentionally internet-accessible by default. When vulnerabilities emerge in common application frameworks such as React and Next.js, attackers face minimal friction. No phishing campaign, no credential theft, and no lateral movement are required; only an exposed service and exploitable condition.
The activity Darktrace observed during the React2shell intrusions reflects techniques that are familiar yet highly effective in cloud-based attacks. Attackers quickly pivot from an exposed internet-facing application to abusing the underlying cloud infrastructure, using automated exploitation to deploy secondary payloads at scale and ultimately act on their objectives, whether monetizing access through cryptomining or to burying themselves deeper in the environment for sustained persistence.
Cloud Case Study
In one incident, opportunistic attackers rapidly exploited an internet-facing Azure virtual machine (VM) running a Next.js application, abusing the React/next.js vulnerability to gain remote command execution within hours of the service becoming exposed. The compromise resulted in the staged deployment of a Go-based remote access trojan (RAT), followed by a series of cryptomining payloads such as XMrig.
Initial Access
Initial access appears to have originated from abused virtual private network (VPN) infrastructure, with the source IP (146.70.192[.]180) later identified as being associated with Surfshark
Figure 1: The IP address above is associated with VPN abuse leveraged for initial exploitation via Surfshark infrastructure.
The use of commercial VPN exit nodes reflects a wider trend of opportunistic attackers leveraging low‑cost infrastructure to gain rapid, anonymous access.
Parent process telemetry later confirmed execution originated from the Next.js server, strongly indicating application-layer compromise rather than SSH brute force, misused credentials, or management-plane abuse.
Payload execution
Shortly after successful exploitation, Darktrace identified a suspicious file and subsequent execution. One of the first payloads retrieved was a binary masquerading as “vim”, a naming convention commonly used to evade casual inspection in Linux environments. This directly ties the payload execution to the compromised Next.js application process, reinforcing the hypothesis of exploit-driven access.
Command-and-Control (C2)
Network flow logs revealed outbound connections back to the same external IP involved in the inbound activity. From a defensive perspective, this pattern is significant as web servers typically receive inbound requests, and any persistent outbound callbacks — especially to the same IP — indicate likely post-exploitation control. In this case, a C2 detection model alert was raised approximately 90 minutes after the first indicators, reflecting the time required for sufficient behavioral evidence to confirm beaconing rather than benign application traffic.
Cryptominers deployment and re-exploitation
Following successful command execution within the compromised Next.js workload, the attackers rapidly transitioned to monetization by deploying cryptomining payloads. Microsoft Defender observed a shell command designed to fetch and execute a binary named “x” via either curl or wget, ensuring successful delivery regardless of which tooling was availability on the Azure VM.
The binary was written to /home/wasiluser/dashboard/x and subsequently executed, with open-source intelligence (OSINT) enrichment strongly suggesting it was a cryptominer consistent with XMRig‑style tooling. Later the same day, additional activity revealed the host downloading a static XMRig binary directly from GitHub and placing it in a hidden cache directory (/home/wasiluser/.cache/.sys/).
The use of trusted infrastructure and legitimate open‑source tooling indicates an opportunistic approach focused on reliability and speed. The repeated deployment of cryptominers strongly suggests re‑exploitation of the same vulnerable web application rather than reliance on traditional persistence mechanisms. This behavior is characteristic of cloud‑focused attacks, where publicly exposed workloads can be repeatedly compromised at scale more easily.
Financial sector spotlight
During the mass exploitation of React2Shell, Darktrace observed targeting by likely North Korean affiliated actors focused on financial organizations in the United Kingdom, Sweden, Spain, Portugal, Nigeria, Kenya, Qatar, and Chile.
The targeting of the financial sector is not unexpected, but the emergence of new Democratic People’s Republic of Korea (DPRK) tooling, including a Beavertail variant and EtherRat, a previously undocumented Linux implant, highlights the need for updated rules and signatures for organizations that rely on them.
EtherRAT uses Ethereum smart contracts for C2 resolution, polling every 500 milliseconds and employing five persistence mechanisms. It downloads its own Node.js runtime from nodejs[.]org and queries nine Ethereum RPC endpoints in parallel, selecting the majority response to determine its C2 URL. EtherRAT also overlaps with the Contagious Interview campaign, which has targeted blockchain developers since early 2025.
Darktrace’s honeypot was exploited just two minutes after coming online, demonstrating how automated scanning, pre-positioned infrastructure and staging, and C2 infrastructure traced back to “bulletproof” hosting reflects a mature, well‑resourced operational chain.
For financial organizations, particularly those operating cloud‑native platforms, digital asset services, or internet‑facing APIs, this activity demonstrates how rapidly geopolitical threat actors can weaponize newly disclosed vulnerabilities, turning short patching delays into strategic opportunities for long‑term access and financial gain. This underscores the need for a behavioral-anomaly-led security posture.
Credit to Nathaniel Jones (VP, Security & AI Strategy, Field CISO) and Mark Turner (Specialist Security Researcher)
Edited by Ryan Traill (Analyst Content Lead)
Appendices
Indicators of Compromise (IoCs)
146.70.192[.]180 – IP Address – Endpoint Associated with Surfshark
