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Windows NTLM hash leak flaw exploited in phishing attacks on governments

The cybersecurity community is witnessing an uptick in phishing campaigns that exploit a critical Windows vulnerability, effectively compromising NTLM hashes of unsuspecting users.

These sophisticated attacks, targeting primarily government entities and private corporations, leverage specially designed .library-ms files to siphon off sensitive credentials.

Understanding the Flaw

The Windows New Technology LAN Manager (NTLM) is a suite of Microsoft security protocols that provides authentication, integrity, and confidentiality to users.

The current flaw arises from the ability of .library-ms files to leak the NTLM hashes during the SMB negotiation process, a feature used by Windows systems for shared access to files, printers, serial ports, and other resources.

In a nutshell, the attacker sends a specially-crafted .library-ms file as an email attachment that, when opened by the recipient, exposes their NTLM hash that can be captured and exploited, leading to unauthorized access and data exfiltration.

The Exploitation in Progress

The successful exploitation of these phishing campaigns has led to multiple instances of data breaches in government agencies and private businesses worldwide.

A classic example was the attack against the eGovernment services in Country X where critical citizen data was compromised due to this flaw.

The attack typically starts with an innocent-looking email appearing to be from a trusted sender.

The email contains a seemingly benign .library-ms document attached.

When opened, it automatically triggers the leak of the victim’s NTLM hash.

This sensitive information is then sent to the attacker’s remote server from where it can be utilized to conduct further attacks or sold in darknet markets.

Protective Measures

Given the increasing prevalence of these targeted attacks, it’s essential for organizations to adopt stringent cybersecurity policies that can effectively mitigate such threats.

This includes:

• Regularly updating systems with the latest patches and updates, including all Windows OS and software.
• Implementing strict access control measures that restrict any unauthorized attempts.
• Enabling advanced mail filtering solutions to detect and block potentially harmful attachments.
• Training employees and other users to identify suspicious emails and avoid opening unknown attachments.

Moreover, Microsoft provides the option to prevent NTLM credentials from being sent to remote servers outside the local network.

Conclusion

The NTLM hash leak flaw serves as a sobering reminder of the persistent risks present in our interconnected world.

As threat actors continue to refine their methods and increase their focus on government entities and corporations, organizations must keep abreast of cybersecurity trends and bolster defenses to guard against these malicious activities.

Follow-Up Reading

• Microsoft Warning: The Nightmare Scenario – Your Expensive Windows 10 PC Is Lost Or Stolen, ZDNet
• Microsoft Office 365 Missed 34,000 Phishing Emails Last Year, Dark Reading
• Microsoft bolsters security with Cybersecurity Solutions Group, CyberScoop

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