Hackers Exploit SharePoint Flaw to Steal Data Undetected

Security researchers have revealed a critical security flaw in Microsoft’s SharePoint collaboration platform. This vulnerability allows hackers to download sensitive files and potentially entire SharePoint sites while cleverly bypassing many standard security systems. The attack leaves minimal traces, making it hard to detect with traditional defenses.

Security experts at Varonis Threat Labs have uncovered two troubling techniques that attackers can leverage. The first involves abusing SharePoint’s “Open in App” feature. Ordinarily, this lets users open documents directly in associated software (like Word or Excel), but attackers can manipulate the underlying code to download files instead. This download looks like a routine access event rather than a security red flag. Hackers can use a PowerShell script to automate the process and siphon large quantities of data.

The second technique is even sneakier. By disguising their activity with the User-Agent string of Microsoft’s SkyDriveSync (now OneDrive) software, attackers can essentially mimic the behavior of the legitimate sync client. This allows for unrestricted downloads of files or whole sites without raising the usual alarms.

This vulnerability is concerning because SharePoint is widely used by businesses to store and share sensitive documents including financial records, intellectual property, and customer data. The subtle nature of these exploits makes them even more dangerous – organizations could be compromised for a long time before realizing they’ve been breached.

Microsoft is undoubtedly working on a patch to address these vulnerabilities. In the meantime, organizations using SharePoint should be on high alert. Careful monitoring of SharePoint logs and network activity for unusual patterns may help detect these attacks. Implementing additional security measures like multi-factor authentication and limiting user permissions on sensitive sites can also mitigate the risk.

Microsoft is likely working on a fix, but in the meantime, companies using SharePoint should be on high alert. It’s crucial to carefully monitor user activity and audit logs for unusual patterns that might indicate abuse of these techniques. Implementing tools that focus on behavioral analysis, rather than just file download detection, could increase the chances of catching these sophisticated attacks.