Attackers are now turning Microsoft 365's built-in trust to their advantage, launching phishing campaigns that operate entirely within the service’s native ecosystem. Instead of relying on fake domains or blatant email spoofing, these sophisticated adversaries are exploiting genuine Microsoft infrastructure, making their phishing emails both convincing and extremely challenging to detect.
• Malicious actors either compromise existing or create new Microsoft 365 organization tenants.
• They set up administrative accounts and mimic legitimate Microsoft transaction notifications.
• By initiating purchase or trial subscription events, the attackers trigger billing emails that appear authentic.
• Once these emails hit the inbox, they provide victims with misleading support contact numbers, steering conversations toward voice channels where fewer security controls exist.
By leveraging genuine Microsoft domains and tenant configurations, these attackers bypass conventional defenses based on DMARC enforcement, domain reputation analysis, and anti-spoofing protocols. The inherent trust in Microsoft’s cloud services turns this into an “inside job” of sorts, making it exceedingly tricky for security teams to spot abnormalities.
J Stephen Kowski, Field CTO at SlashNext, advises that relying solely on native Microsoft 365 protections is no longer sufficient. Instead, he advocates for the deployment of advanced, multi-layered messaging protection solutions that can:
• Detect nuances in tenant manipulation and organizational profile spoofing.
• Analyze communication patterns across channels in real time.
• Automatically remove malicious content from inboxes after delivery.
By incorporating these advanced capabilities, organizations can begin to bridge the gap between conventional anti-phishing measures and the evolving tactics of modern adversaries.
Rom Carmel, CEO at Apono, reinforces the need to limit administrative access. By employing Just-in-Time (JIT) permissions, enterprises can reduce the opportunity for attackers to create rogue administrative accounts or alter tenant settings. This strategy acts as an essential barrier by ensuring that administrative privileges are only granted temporarily, minimizing potential harm from misused access.
Nicole Carignan from Darktrace remarks on the staggering scale of the problem. In their Half-Year Threat Report 2024, Darktrace noted that from December 2023 to July 2024, 17.8 million phishing emails were detected across their customer base. This figure underscores the persistent threat posed by email-based attacks and the dire need for sophisticated, machine learning-powered detection systems.
Lastly, Patrick Tiquet of Keeper Security explains that the misdirection to phone-based scams further complicates threat detection, as such channels are less guarded by the automated and email-centric defenses organizations normally deploy.
• Implement multi-layered messaging protection that extends beyond native Microsoft controls.
• Deploy real-time scanning technology capable of tracking and responding to suspicious behavior immediately after messages are delivered.
• Enforce strict Multi-Factor Authentication (MFA) to secure user accounts and prevent unauthorized access.
• Adopt zero trust principles, continuously verifying user activity and limiting access privileges even for emails coming from trusted Microsoft domains.
• Utilize machine learning-based tools that assess email content, tone, and behavioral patterns, dramatically improving the detection of anomalies indicative of phishing or business email compromise (BEC).
Organizations should not wait for an incident to occur before taking action. A layered security approach that combines advanced threat detection, tight administrative controls, and comprehensive user training is not just recommended—it’s essential. In an era where attackers utilize the very tools meant to facilitate secure communication, a constant re-evaluation of defensive measures is vital.
Stay vigilant, stay updated, and remember that in the modern cybersecurity arena, even trusted infrastructures require constant scrutiny.
Source: Information Security Buzz Targeted Microsoft 365 Tenants: Attackers Exploit Billing Emails For Phishing
Exploiting the Trusted Microsoft Ecosystem
Security researchers at Guardz have uncovered a new wave of malicious campaigns targeting Microsoft 365 tenants. Here’s how the attack unfolds:• Malicious actors either compromise existing or create new Microsoft 365 organization tenants.
• They set up administrative accounts and mimic legitimate Microsoft transaction notifications.
• By initiating purchase or trial subscription events, the attackers trigger billing emails that appear authentic.
• Once these emails hit the inbox, they provide victims with misleading support contact numbers, steering conversations toward voice channels where fewer security controls exist.
By leveraging genuine Microsoft domains and tenant configurations, these attackers bypass conventional defenses based on DMARC enforcement, domain reputation analysis, and anti-spoofing protocols. The inherent trust in Microsoft’s cloud services turns this into an “inside job” of sorts, making it exceedingly tricky for security teams to spot abnormalities.
The Anatomy of the Attack
Traditional phishing scams often rely on glaring red flags—incorrect domains, poor design, or grammatical errors. However, in this scenario, everything appears conventional on the surface. The attackers work from within the ecosystem:- They control multiple Microsoft 365 organization tenants.
- They create realistic administrative accounts that bolster the appearance of legitimacy.
- They craft full-text messages that closely mimic official Microsoft billing communications.
- Finally, they switch the medium from email to voice, exploiting channels that sidestep most technical security controls.
Expert Insights on the Emerging Threat
Industry experts urge organizations not to be complacent. Dor Eisner of Guardz emphasizes that exploiting inherent trust in Microsoft’s cloud services creates significant challenges for security teams tasked with detecting and mitigating such threats. The use of genuine Microsoft infrastructure allows these phishing campaigns to evade many well-established email screening techniques.J Stephen Kowski, Field CTO at SlashNext, advises that relying solely on native Microsoft 365 protections is no longer sufficient. Instead, he advocates for the deployment of advanced, multi-layered messaging protection solutions that can:
• Detect nuances in tenant manipulation and organizational profile spoofing.
• Analyze communication patterns across channels in real time.
• Automatically remove malicious content from inboxes after delivery.
By incorporating these advanced capabilities, organizations can begin to bridge the gap between conventional anti-phishing measures and the evolving tactics of modern adversaries.
Rom Carmel, CEO at Apono, reinforces the need to limit administrative access. By employing Just-in-Time (JIT) permissions, enterprises can reduce the opportunity for attackers to create rogue administrative accounts or alter tenant settings. This strategy acts as an essential barrier by ensuring that administrative privileges are only granted temporarily, minimizing potential harm from misused access.
Nicole Carignan from Darktrace remarks on the staggering scale of the problem. In their Half-Year Threat Report 2024, Darktrace noted that from December 2023 to July 2024, 17.8 million phishing emails were detected across their customer base. This figure underscores the persistent threat posed by email-based attacks and the dire need for sophisticated, machine learning-powered detection systems.
Lastly, Patrick Tiquet of Keeper Security explains that the misdirection to phone-based scams further complicates threat detection, as such channels are less guarded by the automated and email-centric defenses organizations normally deploy.
Strengthening the Defensive Posture
Confronted with these evolving tactics, organizations must transition from a reactive to a proactive security stance. Here are some actionable recommendations:• Implement multi-layered messaging protection that extends beyond native Microsoft controls.
• Deploy real-time scanning technology capable of tracking and responding to suspicious behavior immediately after messages are delivered.
• Enforce strict Multi-Factor Authentication (MFA) to secure user accounts and prevent unauthorized access.
• Adopt zero trust principles, continuously verifying user activity and limiting access privileges even for emails coming from trusted Microsoft domains.
• Utilize machine learning-based tools that assess email content, tone, and behavioral patterns, dramatically improving the detection of anomalies indicative of phishing or business email compromise (BEC).
A Call for Zero Trust and Diligence
The cybersecurity landscape is constantly adapting, and phishing attacks are becoming more sophisticated by the day. The exploitation of Microsoft 365’s trusted infrastructure is a stark reminder that no platform should be assumed to be inherently secure. Both technology and human vigilance must evolve in tandem.Organizations should not wait for an incident to occur before taking action. A layered security approach that combines advanced threat detection, tight administrative controls, and comprehensive user training is not just recommended—it’s essential. In an era where attackers utilize the very tools meant to facilitate secure communication, a constant re-evaluation of defensive measures is vital.
In Summary
The latest phishing campaigns targeting Microsoft 365 emphasize an important lesson: sophistication in cyberattacks is continuous, and trust in well-known platforms can be weaponized against users. By embracing multi-layered security protocols and a zero trust approach, Microsoft 365 tenants can better protect themselves from these emerging threats. Implementing these changes today could mean the difference between a thwarted attempt and a damaging breach tomorrow.Stay vigilant, stay updated, and remember that in the modern cybersecurity arena, even trusted infrastructures require constant scrutiny.
Source: Information Security Buzz Targeted Microsoft 365 Tenants: Attackers Exploit Billing Emails For Phishing
