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Stadia operator dashboard from the seller's listing, showing host and log counters, charts and a world map of infections, as published by Varonis Threat Labs.
Screenshot: Varonis Threat Labs, the Stadia panel dashboard from the seller's listing, Oct. 22, 2026 (fair use).

Detection

Varonis Says StealC's Seller Is Back Four Months After Operation Endgame With Stadia, a RAT That Shares StealC's Code Byte for Byte and Hides a Scheduled Task That Runs Every 15 Minutes

The subscription kit, priced from $300 to $900 a month, wraps the old stealer in hidden desktop control, a command shell, a file explorer and an in-memory loader, and former StealC customers get a free month. Why a rule scoped to schtasks.exe misses it, and the network and host signals that survive every rebuild.

Ava Okello, DetectionLondon6 min read

LONDON - Four months after an international police operation took down StealC, one of the most widely sold password stealers of recent years, the seller behind it is back with something more invasive, according to researchers at Varonis.

The new product, Stadia, was advertised on Oct. 16 as a remote access trojan rather than a stealer. It offers hidden desktop control, a live command shell, a file explorer, a process manager and an in-memory loader, with StealC's stealer attached as one module among six, Varonis Threat Labs wrote in a report updated Thursday. Varonis obtained a build shortly after the listing went up, reversed it and watched the panel operate against a Windows machine of its own.

"The code inside it is StealC's," the researchers wrote.

Back under a new name

Varonis says Europol tore StealC down in June as part of Operation Endgame, with authorities seizing 326 servers and 142 domains and recovering more than 25 million stolen credentials from 385,000 infected machines. The seller, who uses the handle plymouth, rebuilt with a new name, new servers and a new panel.

Stadia sells by monthly subscription: $300 for a basic loader and stealer tier with one build, $550 for a team tier with up to five builds and accounts, and $900 for a Pro tier that adds hidden desktop control, the remote shell, the file explorer and the process manager with no build or account limit. A second post, added a minute after the listing, offers every StealC customer a free month on the Pro tier.

The seller's forum listing titled Stadia - Stealer, Log Restore, Loader, HVNC, File Explorer, describing the modules and stealer targets, as captured by Varonis.
Screenshot: Varonis Threat Labs, the Stadia listing on an underground forum, Oct. 22, 2026 (fair use).

The advertised stealer covers more than 50 browsers, more than 120 crypto plugins and more than 50 desktop wallets, along with messengers, gaming sessions, email clients and VPN clients. The seller's own demo dashboard reports 596 hosts and 496 logs, with infections concentrated in South and Southeast Asia, Africa and Latin America. The panel's changelog lists a first beta on Sept. 10 and a Sept. 29 update that moved the stealer module to StealC 3.5.0.

The proof is in the bytes

The sample Varonis pulled from the builder is a 560,128-byte 32-bit Windows executable with no packer and no Authenticode signature, carrying the build marker STADIA_BETA and agent version 1.1.2. Inside it sits a complete 26,112-byte Chromium App-Bound Encryption helper that Varonis says appears byte for byte in the StealC v3.5 x86 and x64 builds it holds. The log archive the panel produced for the test host used the StealC log format: build.txt, copyright.txt, screenshot.jpg and system_info.txt.

Stadia panel host overview for a test machine, showing status, install path under ProgramData, data counters and the Start Module menu, as captured by Varonis.
Screenshot: Varonis Threat Labs, the Stadia host overview for the researchers' test machine, Oct. 22, 2026 (fair use).

The agent exits on Russian, Ukrainian, Belarusian, Kazakh and Uzbek system languages. Once installed, it calls three hard-coded command-and-control addresses over plain HTTP on port 80, 93.152.213.215, 91.92.43.45 and 193.148.56.97, always in the same order, and waits 300 seconds before starting again if none answer. Each message starts as JSON, is RC4-encrypted and Base64-encoded, and is still sent with a Content-Type of application/json. The operator panel ran at stadiadev[.]cc.

Where detection holds

Varonis says the C2 addresses, RC4 key and access token change with every build, so blocking the three addresses covers only the build it analyzed. What stays the same is the behavior. The agent installs into a randomized 12-character folder under C:\ProgramData using one of nine borrowed names, including RuntimeBroker.exe, MicrosoftEdgeUpdate.exe and AdobeARM.exe. It creates a hidden scheduled task that runs at logon and every 15 minutes for 3,650 days, and when elevated it adds a Microsoft Defender exclusion for its folder with PowerShell's Add-MpPreference.

"The implant registers the task through the Component Object Model (COM) API, so a rule scoped to schtasks.exe would miss it," the researchers wrote.

A Stadia log entry in the panel listing the archive files build.txt, copyright.txt, screenshot.jpg and system_info.txt, the StealC log layout, as captured by Varonis.
Screenshot: Varonis Threat Labs, a Stadia log in the StealC archive format, Oct. 22, 2026 (fair use).

On the host, the clearest sign is the credential theft itself: an unsigned process in C:\ProgramData starts a genuine Chrome, Edge or Brave process suspended and writes a 26 KB block of code into it. Moments later, a .txt file with a GUID-style name appears in C:\ProgramData holding a 64-character hex string, the key the browser uses to protect saved cookies and passwords, and is then deleted.

What defenders can do

  • Alert on Windows Security events 4698 and 4702 where the task XML contains a PT15M interval, a P3650D duration, Hidden set to true and a path under C:\ProgramData, the logic of the Sigma rule Varonis published, and do not limit task monitoring to schtasks.exe.
  • Hunt for new executables in random 12-character folders under C:\ProgramData named after common Windows, Edge, Google, OneDrive, Nvidia or Adobe components, especially when a Defender exclusion for the same folder appears through Add-MpPreference.
  • Flag unsigned processes from C:\ProgramData that launch Chrome, Edge or Brave in a suspended state, and short-lived GUID-named .txt files in C:\ProgramData.
  • On the network, look for HTTP POST requests to the root path of a bare IP address whose Content-Type claims JSON but whose body is Base64 text, and block the three addresses Varonis listed for this build.
  • Start the behavioral rules in alert mode and tune them against your own telemetry before blocking on them, as Varonis advises, and treat any confirmed host as a full credential and session exposure.

Sources:


Ava Okello covers detection engineering, EDR telemetry and SOC hunting for SOCtember from London.

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