In computing, an exclusive lock (also called a deny-read, deny-write lock) prevents any other process from accessing a resource until the locking process releases it. When we say "fsdexe exclusive," we refer to a scenario where a file system filter driver or a process operating at the kernel level has requested and received:

This is more aggressive than a standard shared lock. It bypasses typical user-mode sharing rules.

If you do not have F-Secure installed and see fsd.exe or similar variations in your Task Manager, it could be:

Backup applications (Veeam, Acronis, Windows Server Backup) often use fsdexe exclusive calls when creating Volume Shadow Copies. To ensure a consistent state, the file system driver temporarily suspends write operations to a specific range of sectors, obtaining exclusive control.