A Massive Botnet is Attacking Microsoft365

Brief:

This week, a botnet comprising over 130,000 compromised devices executed coordinated password-spraying attacks against Microsoft 365 (M365) accounts. Security researchers have identified potential links to China-affiliated threat actors, with infrastructure connected to CDS Global Cloud and UCLOUD HK. The botnet employs command-and-control servers hosted by SharkTech, a U.S.-based provider previously associated with malicious activities.

Affected Systems:

• Microsoft 365

What Does This Mean to Me:

Password-spraying attacks are a type of brute-force attack where cybercriminals attempt to gain unauthorized access to multiple accounts by systematically trying a few commonly used passwords across many accounts rather than attempting many passwords on a single account. This gives rise to the importance of a good Password Policy and account controls within Microsoft 365.

Why This Matters for Small Businesses:

Small businesses adopt M365 for its cost-effective and efficient solutions. However, this widespread reliance makes them attractive targets for cybercriminals. The current attack demonstrates that even robust security measures like MFA can be circumvented, leaving sensitive data vulnerable. For small businesses, a successful breach could lead to financial losses, reputational damage, and operational disruptions.

How to Protect Your Business:

• Audit Non-Interactive Sign-Ins — regularly review logs for unauthorized access attempts to identify and respond to suspicious activities.

• Rotate Credentials — change passwords for accounts flagged during security reviews to prevent unauthorized access.

• Disable Legacy Authentication — turn off outdated protocols like Basic Authentication, which are more susceptible to attacks.

• Monitor for Compromised Credentials — keep an eye on infostealer logs and other sources to detect if your organization's credentials have been exposed.

• Implement Conditional Access Policies — set up rules restricting non-interactive login attempts, adding an extra layer of security.

Recommended Response and Countermeasures:

• M365 Systems Admin

With Microsoft planning to retire Basic Authentication by September 2025, small businesses must transition to more secure authentication methods anyway. Proactive steps today can safeguard your business against emerging cyber threats. If you’ve got questions, contact me.

Prepared by:

Russell Mickler
Principal Consultant, Mickler & Associates, Inc.
rmickler@micklerandassociates.com

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