microsoft[.]com

Unit 42 explores modern OAuth threats and actionable steps organizations can take to protect their environments. The post The Current Landscape of OAuth Attacks appeared first on Unit 42 .

Cybersecurity researchers are calling attention to an active device code phishing campaign that's targeting Microsoft 365 identities across more than 340 organizations in the U.S., Canada, Australia, New Zealand, and Germany. The activity, per Huntress, was first spotted on February 19, 2026, with subsequent cases appearing at an accelerated pace since then. Notably, the campaign leverages Cloudflare Workers redirects with captured sessions redirected to infrastructure hosted on a platform-as-a-service (PaaS) offering called Railway, effectively turning it into a credential harvesting engine. Construction, non-profits, real estate, manufacturing, financial services, healthcare, legal, and government are some of the prominent sectors targeted as part of the campaign. "What also makes this campaign unusual is not just the device code phishing techniques involved, but the variety of techniques observed," the company said. "Construction bid lures, landing page code generation, DocuSign impersonation, voicemail notifications, and abuse of Microsoft Forms pages are all hitting the same victim pool through the same Railway.com IP infrastructure." Device code phishing refers to a technique that exploits the OAuth device authorization flow to grant the attacker persistent access tokens, which can then be used to seize control of victim accounts. What's significant about this attack method is that the tokens remain valid even after the account's password is reset. At a high level, the attack works as follows - Threat actor requests a device code from the identity provider (e.g, Microsoft Entra ID) via the legitimate device code API. The service responds with a device code. Threat actor creates a persuasive email and sends it to the victim, urging them to visit a sign-in page ("microsoft[.]com/devicelogin") and enter the device code. After the victim enters the provided code, along with their credentials and two-factor authentication (2FA) code, the service creates an access token and a refresh token for the user. "Once the user has fallen victim to the phish, their authentication generates a set of tokens that now live at the OAuth token API endpoint and can be retrieved by providing the correct device code," Huntress explained. "The attacker, of course, knows the device code because it was generated by the initial cURL request to the device code login API." "And while that code is useless by itself, once the victim has been tricked into authenticating, the resulting tokens now belong to anyone who knows which device code was used in the original request." The use of device code phishing was first observed by Microsoft and Volexity in February 2025, with subsequent waves documented by Amazon Threat Intelligence and Proofpoint. Multiple Russia-aligned groups tracked as Storm-2372, APT29, UTA0304, UTA0307, and UNK_AcademicFlare, have been attributed to these attacks. The technique is insidious, not least because it leverages legitimate Microsoft infrastructure to perform the device code authentication flow, thereby giving users no reason to suspect anything could be amiss. In the campaign detected by Huntress, the authentication abuse originates from a small cluster of Railway.com IP addresses, with three of them accounting for roughly 84% of observed events - 162.220.234[.]41 162.220.234[.]66 162.220.232[.]57 162.220.232[.]99 162.220.232[.]235 The starting point of the attack is a phishing email that wraps malicious URLs within legitimate security vendor redirect services from Cisco, Trend Micro, and Mimecast so as to bypass spam filters and trigger a multi-hop redirect chain featuring a combination of compromised sites, Cloudflare Workers, and Vercel as intermediaries before taking the victim to the final destination. "The observed landing sites prompt the victim to proceed to the legitimate Microsoft device code authentication endpoint and input a provided code in order to read some files," Huntress said. "The code is rendered directly on the page when the victim arrives." "This is an interesting iteration of the tactic, as, normally, the adversary must produce and then provide the code to the victim. By rendering the code directly on the page, likely by some code generation automation, the victim is immediately provided with the code and pretext for the attack." The landing page also comes with a "Continue to Microsoft" that, when clicked, spews a pop-up window rendering the legitimate Microsoft authentication endpoint ("microsoft[.]com/devicelogin"). Almost every device code phishing site has been hosted on a Cloudflare workers[.]dev instance, illustrating how the threat actors are weaponizing the trust associated with the service in enterprise environments to sidestep web content filters. To combat the threat, users are advised to scan sign-in logs to hunt for Railway IP logins, revoke all refresh tokens for affected users, and block authentication attempts from Railway infrastructure if possible. Huntress has since attributed the Railway attack to a new phishing-as-a-service (PhaaS) platform known as EvilTokens, which made its debut last month on Telegram. Besides advertising tools to send phishing emails and bypass spam filters, the EvilTokens dashboard provides customers with open redirect links to vulnerable domains to obscure the phishing links. "In addition to rapid growth in tool functionality, the EvilTokens team has spun up a full 24/7 support team and a support feedback channel," the company said. "They also have customer feedback." The disclosure comes as Palo Alto Networks Unit 42 also warned of a similar device code phishing campaign, highlighting the attack's use of anti-bot and anti-analysis techniques to fly under the radar, while exfiltrating browser cookies to the threat actor on page load. The earliest observation of the campaign dates back to February 18, 2026. The phishing page "disables right-click functionality, text selection, and drag operations," the company said, adding it "blocks keyboard shortcuts for developer tools (F12, Ctrl+Shift+I/C/J) and source viewing (Ctrl+U)" and "detects active developer tools by utilizing a window size heuristic, which subsequently initiates an infinite debugger loop." Update In a follow-up analysis published on March 30, 2026, Sekoia described EvilTokens as a new turnkey Microsoft device code phishing kit that's sold under a PhaaS model since mid-February 2026. It also offers customers self-hosted phishing templates that include - A decoy page that impersonates a Microsoft service or trusted application (e.g., Adobe Acrobat, DocuSign, or SharePoint) as part of phishing emails bearing financial, meeting, logistics, or payroll-related lures. A verification code for the user to copy. Instructions to complete identity verification via Microsoft. A "Continue to Microsoft" button that redirects to the legitimate Microsoft device login page. Thus, when a user copies the verification code and clicks on the "Continue to Microsoft" button, the phishing page launches the legitimate Microsoft device sign-in page in a pop-up window. Once the verification code is entered, they are redirected to the standard Microsoft authentication login page. As soon as the sign-in is complete, the attacker gains access to the victim's account for the targeted service. Campaigns leveraging the PhaaS service have targeted organizations across North, Central, and South America, Europe, the Middle-East, Asia, and Oceania. Among the most affected are the U.S., Australia, Canada, France, India, Switzerland, and the U.A.E. The extensive reach and diversity of these campaigns reflect the rapid adoption of EvilTokens, Sekoia added. "EvilTokens provides a turnkey Microsoft device code phishing kit and a range of advanced features to conduct BEC attacks, including access weaponisation, email harvesting, reconnaissance capabilities, a built-in webmail interface, and AI-powered automation," the French cybersecurity company said. "The EvilTokens PhaaS operates through fully featured bots on Telegram and continuously improves its phishing kit with new capabilities. In the near future, the operator intends to extend support to Gmail and Okta phishing pages." (The story was updated after publication on March 31, 2026, to include additional details of EvilTokens.)

Introduction In the latter half of 2024, the Russian IT industry, alongside a number of entities in other countries, experienced a notable cyberattack. The attackers employed a range of malicious techniques to trick security systems and remain undetected. To bypass detection, they delivered information about their payload via profiles on both Russian and international social media platforms, as well as other popular sites supporting user-generated content. The samples we analyzed communicated with GitHub, Microsoft Learn Challenge, Quora, and Russian-language social networks. The attackers thus aimed to conceal their activities and establish a complex execution chain for the long-known and widely used Cobalt Strike Beacon. Although the campaign was most active during November and December 2024, it continued until April 2025. After a two-month silence, our security solutions began detecting attacks again. The adversary employed new malicious samples, which were only slightly modified versions of those described in the article. Kaspersky solutions detect this threat and assign the following verdicts: HEUR:Trojan.Win64.Agent.gen HEUR:Trojan.Win64.Kryptik.gen HEUR:Trojan.WinLNK.Starter.gen MEM:Trojan.Multi.Cobalt.gen HEUR:Trojan.Win32.CobaltStrike.gen Initial attack vector The initial attack vector involved spear phishing emails with malicious attachments. The emails were disguised as legitimate communications from major state-owned companies, particularly within the oil and gas sector. The attackers feigned interest in the victims’ products and services to create a convincing illusion of legitimacy and increase the likelihood of the recipient opening the malicious attachment. All attachments we observed were RAR archives with the following structure: Требования.lnk Требования - Company Profile.pdf - List of requirements.pdf - Требования Company profile.pdf and List of requirements.pdf were decoy files designed to complement the information in the email. The directory Требования\Требования contained executables named Company.pdf and Requirements.pdf, designed to mimic secure PDF documents. The directory itself was hidden, invisible to the user by default. When Требования.lnk was opened, the files in Требования\Требования were copied to %public%\Downloads\ and renamed: Company.pdf became nau.exe, and Requirements.pdf became BugSplatRc64.dll. Immediately afterward, nau.exe was executed. Contents of Требования.lnk Malicious agent In this attack, the adversary leveraged a common technique: DLL Hijacking (T1574.001). To deploy their malicious payload, they exploited the legitimate Crash reporting Send Utility (original filename: BsSndRpt.exe). The tool is part of BugSplat, which helps developers get detailed, real-time crash reports for their applications. This was the utility that the attackers renamed from Company.pdf to nau.exe. For BsSndRpt.exe to function correctly, it requires BugSplatRc64.dll. The attackers saved their malicious file with that name, forcing the utility to load it instead of the legitimate file. To further evade detection, the malicious BugSplatRc64.dll library employs Dynamic API Resolution (T1027.007). This technique involves obscuring API functions within the code, resolving them dynamically only during execution. In this specific case, the functions were obfuscated via a custom hashing algorithm, which shares similarities with CRC (Cyclic Redundancy Check). A significant portion of the hashes within the malicious sample are XOR-encrypted. Additionally, after each call, the address is removed from memory, and API functions are reloaded if a subsequent call is needed. MessageBoxW function hook The primary purpose of BugSplatRc64.dll is to intercept API calls within the legitimate utility’s process address space to execute its malicious code (DLL Substitution, T1574.001). Instead of one of the API functions required by the process, a call is made to a function (which we’ll refer to as NewMessageBox) located within the malicious library’s address space. This technique makes it difficult to detect the malware in a sandbox environment, as the library won’t launch without a specific executable file. In most of the samples we’ve found, the MessageBoxW function call is modified, though we’ve also discovered samples that altered other API calls. After modifying the intercepted function, the library returns control to the legitimate nau.exe process. NewMessageBox function Once the hook is in place, whenever MessageBoxW (or another modified function) is called within the legitimate process, NewMessageBox executes. Its primary role is to run a shellcode, which is loaded in two stages. First, the executable retrieves HTML content from a webpage located at one of the addresses encrypted within the malicious library. In the sample we analyzed, these addresses were https://techcommunity.microsoft[.]com/t5/user/viewprofilepage/user-id/2631 and https://www.quora[.]com/profile/Marieformach. The information found at both locations is identical. The second address serves as a backup if the first one becomes inactive. NewMessageBox searches the HTML code retrieved from these addresses for a string whose beginning and end match patterns that are defined in the code and consist of mixed-case alphanumeric characters. This technique allows attackers to leverage various popular websites for storing these strings. We’ve found malicious information hidden inside profiles on GitHub, Microsoft Learn Challenge, Q&A websites, and even Russian social media platforms. While we didn’t find any evidence of the attackers using real people’s social media profiles, as all the accounts were created specifically for this attack, aligning with MITRE ATT&CK technique T1585.001, there’s nothing stopping the threat actor from abusing various mechanisms these platforms provide. For instance, malicious content strings could be posted in comments on legitimate users’ posts. The extracted payload is a base64-encoded string with XOR-encrypted data. Decrypted, this data reveals the URL https://raw.githubusercontent[.]com/Mariew14/kong/master/spec/fixtures/verify-prs, which then downloads another XOR-encrypted shellcode. We initially expected NewMessageBox to execute the shellcode immediately after decryption. Instead, nau.exe launches a child process with the same name and the qstt parameter, in which all of the above actions are repeated once again, ultimately resulting in the execution of the shellcode. Shellcode An analysis of the shellcode (793453624aba82c8e980ca168c60837d) reveals a reflective loader that injects Cobalt Strike Beacon into the process memory and then hands over control to it (T1620). The observed Cobalt sample communicates with the C2 server at moeodincovo[.]com/divide/mail/SUVVJRQO8QRC. Attribution and victims The method used to retrieve the shellcode download address is similar to the C2 acquisition pattern that our fellow security analysts observed in the EastWind campaign. In both cases, the URL is stored in a specially crafted profile on a legitimate online platform like Quora or GitHub. In both instances, it’s also encrypted using an XOR algorithm. Furthermore, the targets of the two campaigns partially overlap: both groups of attackers show interest in Russian IT companies. It’s worth mentioning that while most of the attacks targeted Russian companies, we also found evidence of the malicious activity in China, Japan, Malaysia, and Peru. The majority of the victims were large and medium-sized businesses. Takeaways Threat actors are using increasingly complex and clever methods to conceal long-known tools. The campaign described here used techniques like DLL hijacking, which is gaining popularity among attackers, as well as obfuscating API calls within the malicious library and using legitimate resources like Quora, GitHub, and Microsoft Learn Challenge to host C2 addresses. We recommend that organizations adhere to the following guidelines to stay safe: Track the status of their infrastructure and continuously monitor their perimeter. Use powerful security solutions to detect and block malware embedded within bulk email. Train their staff to increase cybersecurity awareness. Secure corporate devices with a comprehensive system that detects and blocks attacks in the early stages. You can detect the malware described here by searching for the unsigned file BugSplatRc64.dll in the file system. Another indirect sign of an attack could be the presence of Crash reporting Send Utility with any filename other than the original BsSndRpt.exe. IOCs: LNK 30D11958BFD72FB63751E8F8113A9B04 92481228C18C336233D242DA5F73E2D5 Legitimate BugSplat.exe 633F88B60C96F579AF1A71F2D59B4566