A new phishing campaign has been observed leveraging Google Apps Script to deliver deceptive content designed to extract Microsoft 365 login credentials from unsuspecting users. This method utilizes a trusted Google platform to lend credibility to malicious links, thereby increasing the likelihood of user interaction and credential theft.
Google Apps Script is a cloud-based scripting language developed by Google that allows users to extend and automate the functions of Google Workspace applications such as Gmail, Sheets, Docs, and Drive. Built on JavaScript, this tool is commonly used for automating repetitive tasks, creating workflow solutions, and integrating with external APIs.
In this specific phishing operation, attackers create a fraudulent invoice document, hosted through Google Apps Script. The phishing process typically begins with a spoofed email appearing to notify the recipient of a pending invoice. These emails contain a hyperlink, ostensibly leading to the invoice, which uses the “script.google.com” domain. This domain is an official Google domain used for Apps Script, which can deceive recipients into believing that the link is safe and from a trusted source.
The embedded link directs users to a landing page, which may include a message stating that a file is available for download, along with a button labeled “Preview.” Upon clicking this button, the user is redirected to a forged Microsoft 365 login interface. This spoofed page is designed to closely replicate the legitimate Microsoft 365 login screen, including layout, branding, and user interface elements.
Victims who do not recognize the forgery and proceed to enter their login credentials inadvertently transmit that information directly to the attackers. Once the credentials are captured, the phishing page redirects the user to the legitimate Microsoft 365 login site, creating the illusion that nothing unusual has occurred and reducing the chance that the user will suspect foul play.
This redirection technique serves two main purposes. First, it completes the illusion that the login attempt was routine, reducing the likelihood that the victim will report the incident or change their password promptly. Second, it hides the malicious intent of the earlier interaction, making it harder for security analysts to trace the event without in-depth investigation.
The abuse of trusted domains such as “script.google.com” presents a significant challenge for detection and prevention mechanisms. Emails containing links to reputable domains often bypass basic email filters, and users are more inclined to trust links that appear to come from platforms like Google. This type of phishing campaign demonstrates how attackers can manipulate well-known services to bypass conventional security safeguards.
The technical foundation of this attack relies on Google Apps Script’s web app capabilities, which allow developers to create and publish web applications accessible via the script.google.com URL structure. These scripts can be configured to serve HTML content, handle form submissions, or redirect users to other URLs, making them suitable for malicious exploitation when misused.
From an attacker’s perspective, hosting content via a legitimate Google domain offers several advantages. It enhances the perceived legitimacy of the link, aids in bypassing URL-based security filters, and masks the origin of the content. Since the service is widely used in enterprise environments for legitimate automation, the malicious use of the platform blends in with normal traffic patterns, further complicating detection.
The implications of successful credential harvesting via this method are substantial. With access to Microsoft 365 accounts, threat actors may obtain sensitive organizational data, impersonate users for further phishing attacks, or exfiltrate documents stored in OneDrive or SharePoint. Additionally, they may attempt to pivot deeper into organizational networks or initiate business email compromise (BEC) attacks targeting financial transactions.
This campaign highlights a broader trend in phishing tactics, where attackers increasingly exploit the infrastructure of well-known platforms to distribute malicious content. These campaigns are typically part of a larger strategy to compromise enterprise environments, bypass perimeter defenses, and gain unauthorized access to cloud-based services.
Mitigation of such threats involves a multi-layered approach. Organizations are advised to implement advanced threat protection systems capable of analyzing the behavior of linked content, even when hosted on trusted domains. Endpoint protection, anomaly detection, and continuous user education form the core components of an effective defense strategy.
Security awareness remains a critical factor in mitigating the risks posed by phishing. Users should be trained to critically evaluate email content, inspect URLs before clicking, and avoid entering credentials on unfamiliar pages. Multi-factor authentication (MFA) adds an essential layer of protection, as it prevents account compromise even if credentials are harvested.
From a technical administration standpoint, organizations should monitor the use of Google Apps Script within their environment, particularly if users are permitted to publish scripts as web applications. Restrictions can be configured to limit script execution or prevent external publishing, reducing the risk of misuse.
Cloud service providers are also encouraged to implement safeguards that detect and flag suspicious uses of their platforms. This may include monitoring for abnormal publishing behavior, identifying phishing-related patterns in script content, and proactively disabling malicious scripts.
As phishing tactics continue to evolve, so too must the strategies employed to defend against them. The abuse of platforms like Google Apps Script underscores the importance of adaptive security practices that go beyond simple blacklisting or domain-based filtering. Vigilance, automation, and continuous improvement of detection methodologies are necessary to counter the growing sophistication of phishing operations.