Russian Hackers Hijack Hotel Wi-Fi to Steal Microsoft 365 Tokens

Microsoft says Russian hackers hijacked hotel Wi-Fi portals to spread malware and steal Microsoft 365 tokens from travelers.

Microsoft Threat Intelligence disclosed CaptiveCrunch, a campaign it attributes to Storm-2945, an operational sub-cluster of Midnight Blizzard, the Russian SVR-linked group also known as APT29 and Cozy Bear. Since early May 2026, Storm-2945 has been manipulating DNS and HTTP traffic on captive portal networks at hotels, conference centers, and shared venues worldwide to redirect guests toward malware and credential theft operations. If you connected to hotel Wi-Fi while traveling in the past few months, this report is worth reading carefully.

“Since early May 2026, Microsoft Threat Intelligence has observed Storm-2945 manipulating DNS and HTTP traffic from networks served by captive portals to redirect user traffic through actor-controlled infrastructure.” reads the report published by Microsoft. “To date, Microsoft has identified widespread compromise of Wi-Fi networks at hospitality-related organizations and other networks serviced by captive portal equipment in several countries. ReliaQuest has identified this activity not only at hotels, but also conference centers and other shared venues, and assesses that the goal of this activity is to access the accounts of corporate travelers.”

That last point matters: the shared infrastructure patterns suggest this may not be a series of individual venue compromises but rather access to something shared across portions of the captive portal ecosystem. Microsoft hasn’t named any provider.

The malware delivered through these networks is CornFlake, a full-featured Windows remote access trojan written in Go.

“CornFlake registers as a Windows service named svchost32 with the display name “Cloud Sync Service” and description “Synchronizes files with the cloud storage provider”, deliberately mimicking the legitimate svchost.exe process.” continues the report. “It establishes redundant persistence mechanisms: Windows service registrations, Registry Run keys, named scheduled tasks, and a persistence watchdog routine that runs continuously to restore any persistence mechanism that is removed by defenders or endpoint protection.”

CornFlake establishes an encrypted C2 channel using ECDH P-256 key exchange and supports dynamic reconfiguration without redeployment. Once installed, the RAT can log keystrokes, monitor the clipboard, capture screenshots, audio and webcam feeds, steal browser credentials, exfiltrate files, monitor USB devices, collect detailed system information, and execute remote commands. It also exposes a local HTTP API, allowing companion malware such as ChocoShell to reuse its secure C2 channel for file theft, configuration updates, and connectivity checks.

“For command and control (C2), CornFlake performs an Elliptic Curve Diffie-Hellman (ECDH) P-256 ephemeral key exchange with the C2 server, derives a session key via SHA-256, and communicates over a custom JSON protocol framed within the encrypted channel.” states the report. “This provides an encrypted channel to the C2 server, with each C2 session using a unique ephemeral key, making decryption of captured traffic impossible without the session-specific private key. “

Each C2 session uses a unique ephemeral key, which means captured traffic can’t be decrypted without that session’s private key. The malware also supports a runtime configuration file that lets the attacker reconfigure C2 servers and targeting without redeploying the implant.

CornFlake is delivered via ClickFix-style pages that impersonate Windows Update screens, Google verification pages, DirectX installers, browser update prompts, and disk optimization utilities — whatever looks most plausible for the venue. The victim still has to execute the payload, but the captive portal controls exactly what they see when they try to connect. Microsoft also found indications that Storm-2945 may be targeting Android devices through the same landing pages, which include instructions to download and install an APK.

The second tool, ChocoShell, is a PowerShell infostealer that runs entirely in memory. Its primary target is credentials.

“ChocoShell collects Microsoft 365 and Azure Active Directory (AD) access tokens, refresh tokens, and Web Account Manager (WAM) tokens from .tbres files in the Token Broker cache. Collection of these tokens represents a significant threat to enterprise environments, as threat actors could replay SSO sessions without browser cookies.” states Microsoft. “Additionally, Wi-Fi credentials are harvested via netsh wlan show profile with key=clear.”

ChocoShell also implements three silent UAC bypass techniques with ordered fallback, disables Windows Defender signature updates, and uses Chrome DevTools Protocol to extract browser cookies by launching the browser with a remote debugging port. This technique bypasses Chrome’s App-Bound Encryption entirely.

Since July 16, some CaptiveCrunch landing pages have added device code phishing to the mix, redirecting guests into Microsoft’s legitimate device code authentication flow. The attacker initiates the authentication request and presents the user with a code to enter at Microsoft’s real sign-in page. When the user enters it, they authenticate the attacker’s session instead of their own — an MFA-satisfied session, since the user just completed the factor. Microsoft recommends blocking the device code flow through Conditional Access policies everywhere it isn’t explicitly required.

Researchers also detailed FruitStone, the web-based C2 panel used by Storm-2945 operators to manage the CaptiveCrunch campaign. It provides a centralized interface to control CornFlake implants, deploy payloads, collect stolen data, and manage compromised devices. Disguised as a legitimate “CloudSync Console,” it supports multi-operator access, agent monitoring, remote commands, file theft, credential collection, configuration updates, and campaign infrastructure management.

The practical advice for travelers is blunt: treat hotel, conference, and airport Wi-Fi as hostile. Use a mobile hotspot or cellular data instead wherever possible. Don’t download or execute anything a captive portal presents as an update, certificate, troubleshooting tool, or security utility. Don’t enter corporate credentials on venue registration pages. And if your organization hasn’t already blocked device code flow in Conditional Access, now is a reasonable time to check.

Recently, ReliaQuest’s threat research team also documented attackers compromising the Wi-Fi gateways at hotels and conference centers, then quietly rerouting guests toward fake Microsoft login pages.

There’s a pattern connecting all this to previous campaigns. The tradecraft echoes a Russian-linked operation called FrostArmada, which hit home routers the same way earlier this year, and researchers tie both to the group known as APT28 (aka UAC-0001, aka Fancy Bear, Pawn Storm, Sofacy Group, Sednit, BlueDelta, and STRONTIUM). The link isn’t a smoking gun; it’s shared technique, not shared infrastructure, and the researchers say so plainly.

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Pierluigi Paganini

(SecurityAffairs – hacking, Hotel Wi-Fi)