Which file system does NOT have built-in security features for controlling user access?

FAT32 is the correct choice because this file system was designed in the early days of computing, primarily for compatibility with older operating systems and to support larger disks than its predecessor, FAT16. It does not include any built-in security features that are inherent to more modern file systems, such as access control lists (ACLs) or file permissions that specify which users can read, write, or execute files.

In contrast, NTFS (New Technology File System) has sophisticated security features, including user access control and file encryption options. Similarly, exFAT, while intended for flash drives, also lacks some features compared to NTFS, it still provides better compatibility and larger file size handling compared to FAT32, but is less robust in terms of security capabilities. ext4 is a journaling file system utilized mainly in Linux environments that includes comprehensive security features like ACLs.

Therefore, FAT32 stands out as the only file system among the options presented that lacks built-in mechanisms for controlling user access.