Microsoft has warned that hotel, conference, and other hospitality Wi-Fi networks are being actively abused by a Russian group to target travelers worldwide. The campaign, dubbed “CaptiveCrunch” turns a routine Wi-Fi login moment into an opportunity to compromise corporate accounts and devices.

From the user’s perspective, nothing looks out of the ordinary: they connect to hotel Wi-Fi, get the usual captive portal prompt, and perhaps see a familiar‑looking message about needing to update something before they can browse. However, behind the scenes, the allegedly state-linked group position themselves in the network path and manipulate DNS (Domain Name System) and HTTP traffic from captive‑portal Wi-Fi.

From there, several things can happen:

• Logins are stolen: The user’s browser session is redirected to attacker‑controlled phishing pages, like fake Microsoft login prompts, where credentials, device codes, or OAuth tokens are harvested.
• Malware is downloaded: The user is presented with fake update or ClickFix dialogs that download malware. In these cases, usually a remote access trojan (RAT) plus an infostealer.
• A machine-in-the-middle attack (MitM) where traffic is quietly proxied through attacker infrastructure, putting the user in a position for further credential theft.

Reportedly, one of the main malware strains used in these attacks is called CornFlake,  a remote access trojan (RAT) that can capture webcam images, microphone audio, and keystrokes.

The infostealer was identified as ChocoShell, a fileless Powershell-based information stealer which primarily goes after browser session cookies, saved passwords, Microsoft 365 Single Sign-On (SSO) tokens, and Wi-Fi credentials from compromised systems.

Microsoft lists a set of fake dialogs that may appear once you connect to compromised Wi‑Fi:

• winupdate: A bogus Windows Update window with “Working on updates… Don’t turn off your computer.”
• defender: A fake Windows Security virus scan.
• directx: “DirectX End‑User Runtime Web Installer.”
• vcredist: A Microsoft Visual C++ redistributable installer.
• sysopt: A disk optimization utility.
• netfix: A Windows Network Diagnostics ‘fix’ tool.
• browser: A browser update prompt.
• pdfview: A document/PDF viewer installer.

How to stay safe

Malwarebytes has long warned about the safety of public Wi-Fi. Here’s how you can stay safe while traveling:

• Use your own phone’s hotspot instead of using the public Wi‑Fi. A mobile connection, especially with an eSIM and a reputable carrier, significantly reduces the likelihood of an attack compared to an unknown hotel network.
• If you’re forced to use public Wi‑Fi, use a VPN with an active Kill Switch: Complete the authentication on the hotel portal first, then launch your VPN before opening any website or app. The Kill Switch feature will instantly block all internet traffic if the VPN disconnects even for a second, preventing cybercriminals from injecting malicious code out in the open. While CaptiveCrunch operates around captive portals and pre‑VPN flows, a VPN still reduces other risks and limits passive data collection once you’re online.
• Always inspect the certificate of any public Wi‑Fi login or ‘security’ portal that asks for more than a room number or basic credentials. These aren’t always a straight‑up giveaway, but sometimes they can be an obvious clue: mismatched hostnames, untrusted issuers, or plain HTTP are red flags that should stop you from proceeding.
• Many captive portals ask for an email address for registration or marketing. Even in benign cases, there is little value in handing over your real inbox. If you must provide an address, consider giving a fake one or a throwaway alias that is unrelated to your primary accounts.
• If you are asked to download software, a certificate, a browser update, or a fix tool in order to connect, stop. You should never have to download anything just to log into Wi‑Fi.
• Don’t rush to follow instructions on a webpage or prompt, especially if it asks you to run commands on your device or copy-paste code. Be cautious of pages urging immediate action: sophisticated ClickFix pages add countdowns, user counters, or other pressure tactics to make you act quickly.
• Secure your devices. Use an up-to-date, real-time anti-malware solution with a web protection component.
• Avoid entering Microsoft 365, Google Workspace, or other high‑value credentials directly into any page reached via captive portal redirection. If you need to check corporate mail, follow known URLs rather than clicking through prompts.

And last but not least, update your browser, operating systems, and other important software before you travel. That reduces the chance of getting legitimate update requests while you’re away.

From reporting threats to removing them.

Cybersecurity risks should never spread beyond a headline. Keep threats off your devices by downloading Malwarebytes today.

Storm-2945 Uses Hospitality Networks to Target Travelers 

Credential Theft and Malware Deployment 

AI-Assisted Malware and Centralized Control

Microsoft's Defensive Guidance

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)