Concerning a development, cybersecurity experts at Proofpoint have uncovered an ongoing targeted phishing campaign that has successfully compromised the accounts of hundreds of Microsoft Office and Azure users, including those of senior executives. This campaign, still active, employs individualized phishing lures embedded within shared documents, deceiving users into clicking links that redirect them to malicious phishing web pages.
The attackers have cast a wide net, targeting a diverse range of individuals across various organizations globally. The affected user base includes Sales Directors, Account Managers, Finance Managers, and high-ranking executives such as Vice Presidents of Operations, Chief Financial Officers, Treasurers, Presidents, and CEOs. The strategic selection of targets across different organizational functions suggests a calculated approach by threat actors to access valuable resources and information.
Key Indicator of the Phishing Campaign:
User-Agent String: Attackers use a specific user-agent string during the access phase of the attack chain. - String Details: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36
Primary Use: This user-agent is predominantly utilized to gain unauthorized access to native Microsoft 365 apps, including:
1. 'OfficeHome' Sign-in Application: Used for initial login attempts.
2. ' Office 365 Exchange Online': Targeted for post-compromise mailbox abuse.
3. 'My Signins': Exploited for manipulating multifactor authentication (MFA).
The initial success in accessing accounts often leads to a series of unauthorized activities, such as downloading sensitive files, sending fraudulent emails, and creating obfuscation rules to conceal their tracks. Notably, attackers have been observed manipulating MFA by registering alternative phone numbers or adding mobile authenticator apps to maintain persistent access.
To counteract this sophisticated phishing campaign, Proofpoint urges IT and information security leaders to implement several defensive measures:
- Monitor Logs: Keep an eye on specific user agent strings and source domains in your organization's logs to detect potential threats.
- Change Credentials: Promptly change credentials for compromised and targeted users and enforce periodic password changes for all users.
- Identify Account Takeovers: Use security solutions to accurately detect initial account compromises and post-compromise activities, ensuring visibility into abused services and applications.
- Identify Threat Vectors: Pinpoint's initial threat vectors include email-borne threats like phishing, malware, and impersonation, as well as brute-force attacks and password-spraying attempts.
- Employ Auto-remediation: Implement policies to reduce attackers' dwell time and minimize potential damages.
By staying vigilant and adopting these proactive measures, organizations can enhance their cybersecurity posture and protect their valuable assets from this sophisticated phishing campaign targeting senior executives.
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