Hackers Exploit Exposed ASP.NET Keys to Deploy Malware

Exposed ASP.NET Keys: A Growing Cyber Threat

Cybercriminals are actively exploiting publicly exposed ASP.NET machine keys to launch malicious ViewState code injection attacks. By leveraging these static keys, attackers can deploy malware like the Godzilla post-exploitation framework, potentially compromising entire systems. With over 3,000 exposed keys identified by Microsoft, this poses a serious and immediate security risk for developers and organizations. 

How Attackers Exploit ViewState Code Injection

ASP.NET machine keys (validationKey and decryptionKey) ensure the integrity of ViewState data by preventing tampering and unauthorized access. However, some developers mistakenly copy keys from public repositories, unwittingly opening the door for cyberattacks.

The Attack Chain:

• Attackers obtain machine keys from publicly available sources like code repositories.
• They craft a malicious ViewState with a message authentication code (MAC) using the stolen key.
• The infected ViewState is sent via a POST request to an IIS web server.
• The ASP.NET Runtime validates and decrypts the malicious ViewState, executing the attacker's code.
• The attacker gains Remote Code Execution (RCE), allowing them to deploy further payloads.

Real-World Impact: Godzilla Framework Deployment

In December 2024, Microsoft detected threat actors using this technique to inject the Godzilla post-exploitation framework. Godzilla enables malicious command execution and shellcode injection, posing a severe risk to IIS web servers. Unlike stolen keys sold on dark web forums, these publicly disclosed keys are easily accessible, making them more dangerous.

How to Protect Your Systems

Microsoft and cybersecurity experts recommend the following mitigation steps:

Secure Machine Key Management

• Never use public or default keys. Always generate unique, secure keys.
• Encrypt machine keys. Protect sensitive data like the machineKey and connectionStrings elements to prevent plaintext exposure.
• Regularly rotate keys. Update machine keys periodically to minimize security risks.

System Hardening

• Upgrade to ASP.NET 4.8. Enable Antimalware Scan Interface (AMSI) to detect suspicious activity.
• Apply attack surface reduction rules. Block web shell creation to reduce exploitation chances.
• Audit and monitor configuration files. Track unauthorized changes to web.config and machine.config files.

Incident Response

• Use Microsoft Defender for Endpoint. Identify publicly disclosed keys with alert systems.
• Deploy Microsoft Sentinel. Leverage threat intelligence analytics to detect ViewState-based attacks.
• Investigate compromised servers. If an attack is detected, perform a full forensic analysis and consider system reinstallation.

Final Thoughts

The exploitation of exposed ASP.NET machine keys for ViewState code injection attacks is a critical and escalating cybersecurity threat. With over 3,000 exposed keys identified, the risk to businesses and developers is more significant than ever. These attacks enable remote code execution (RCE), allowing hackers to deploy dangerous malware like the Godzilla post-exploitation framework, potentially compromising entire systems.

Organizations can no longer afford to overlook secure key management and system hardening. Implementing unique, encrypted, and regularly rotated machine keys, upgrading security frameworks, and leveraging real-time threat detection tools are essential steps in mitigating these attacks.

Cyber threats evolve rapidly, and staying ahead requires vigilance, proactive defense strategies, and a commitment to security best practices. By securing your ASP.NET applications today, you can prevent tomorrow’s breaches.

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