SharePoint Backdoor Scanner

Microsoft SharePoint is a widely used web-based collaborative platform that integrates with Microsoft Office. It is typically employed by organizations for document management, storage, and communication, facilitating team collaboration and information sharing. SharePoint's versatile capabilities allow it to be used across various industries, from business to education, providing tools for internal portals, enterprise search, and intranet functionalities. Due to its extensive integration features, SharePoint is often connected with other enterprise systems, making it an integral part of business processes. Security is paramount as SharePoint handles sensitive data, requiring robust measures to protect against unauthorized access. Its configurability and extensibility also demand vigilant management to prevent security loopholes.

The vulnerability in question involves the presence of a backdoor, specifically a webshell, in Microsoft SharePoint. This security issue is critical because it can lead to unauthorized control over the SharePoint server, allowing attackers to execute arbitrary commands. The backdoor leverages a file named 'spinstall0.aspx', exposing cryptographic machineKey values which are sensitive configuration elements in SharePoint. This type of vulnerability is often exploited in post-authentication remote code execution (RCE) scenarios. The backdoor is an indicator of a larger, targeted attack campaign aimed at compromising SharePoint servers. Prompt detection and remediation are crucial to maintain the integrity and security of affected systems.

The vulnerability detailed here involves specific technical indicators, such as the presence of certain cryptographic elements in the SharePoint configuration file. The malicious file 'spinstall0.aspx' can be detected by checking for requests to this endpoint. Additionally, characteristics like the file's response size and the presence of specific headers like "microsoftsharepointteamservices" are important detection parameters. The endpoint reveals sensitive machineKey values, which should not be publicly accessible. Methodical verification includes matching the response body contents to known malicious patterns. These technical specifics are critical for security personnel to understand and monitor for effective detection and prevention.

If exploited by malicious actors, this vulnerability can lead to severe breaches of the SharePoint server's security. Potential impacts include unauthorized access to sensitive data and configurations, data exfiltration, and extensive server compromise. Once a backdoor is installed, attackers may maintain persistent access, further exploiting the system for broader network intrusion. Such a scenario can result in significant data loss, reputational damage, and even legal consequences. It also opens pathways for further attacks, such as spreading malware or initiating denial-of-service attacks to disrupt organizational operations.

REFERENCES

• https://research.eye.security/sharepoint-under-siege/