WebDAV

Introduced in 1996, WebDAV (Web Distributed Authoring and Versioning) is a set of extensions to the Hypertext Transfer Protocol (HTTP), which allows users to create, change and move documents on a server (https://en.wikipedia.org/wiki/WebDAV).

WebDAV has been implemented by many vendors to faciliate the transfer of data, such as:-

https://help.sap.com/docs/BS_CA/7ce8e5dc89d7407e8baa9de7b775f31f/019142b5caa241cd8e38c7608282e12c.html
https://documentation.b2c.commercecloud.salesforce.com/DOC1/index.jsp?topic=%2Fcom.demandware.dochelp%2Fcontent%2Fb2c_commerce%2Ftopics%2Fimport_export%2Fb2c_using_web_dav.html
https://www.qnap.com/en/how-to/faq/article/how-to-connect-to-nas-with-webdav-in-windows-by-raidrive
https://mailfence.com/en/doc/documents.jsp

Using Cybersecurity controls to block access to online resources based upon Categorisation, Deny Lists, Firewall rules etc is not effective as Data Loss Prevention technologies.
For users who have the capability to use WebDAV methods, the use of this upload method demonstrates they can easily move sensitive/confidential data outside of organisations.

Supporting legacy technologies increases the scope by which data can be transferred out of organisations, and the associated likelihood of a Data Loss risk event occurring must be considered.
The impact of a Data Loss risk event will depend on the content and amount of information that has been uploaded via the WebDAV method.

Use DLP-TEST to assess: - 

- Coverage of DLP Technologies to detect data being uploaded via the WebDAV method.
- Capability of DLP Technologies to accurately detect sensitive/confidential data being uploaded via the WebDAV method.
- Ability of DLP technologies to ignore data being uploaded that is NOT sensitive or confidential.