Shared Account in the Digital Library
A school digital library uses one Windows file server with NTFS for 30 student PCs. The D: drive has four folders: Public, Projects, Archive, and Exams. All students log in to every PC with one shared local account, student, which has Full Control on D:. Teachers use separate accounts. A student volunteer moved the whole Projects\Class9 folder into Public; later a teacher deleted 20 GB of past papers from Archive and emptied the Recycle Bin. The server has 5 GB free. A weekly full backup copies D: to one external USB hard disk, but no one has restored from it. The librarian wants students to submit work into Projects without deleting other groups’ files, to read Archive, and to keep Exams invisible to students. The school cannot buy new software and has only built-in Windows tools and one spare external disk.
1. Design a group and NTFS permission scheme and explain why the shared student account makes the current rules unenforceable.
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Remove Full Control from the shared account and give permissions to local groups, not directly to people where possible. Suggested scheme:
| Folder | Students group | Teachers group |
|---|---|---|
| Public | Read + Write (no Delete) | Modify |
| Projects\Class9 | Read + Write on own class folder; Creator Owner full control on own subfolder | Modify |
| Archive | Read & Execute | Modify |
| Exams | No access | Modify |
NTFS ‘Write’ allows creating files/folders but not deleting them, which matches the submission rule; ‘Modify’ includes delete, so teachers can manage. The shared student account is the main defect: permissions attach to the account, so every student inherits Full Control and no action is attributable. Even a perfect ACL cannot distinguish one student from another. Use individual accounts, or at minimum separate class accounts, and audit the Projects submissions.
2. Explain which permissions allowed the folder move and the Archive deletion. Give immediate recovery steps.
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On the same NTFS volume, moving a folder is a rename. It requires delete permission on the source and write permission at the destination; Full Control grants both. On Archive, the teacher’s Modify permission includes Delete, so the 20 GB could be removed, and emptying the Recycle Bin removed the easy recovery path.
Immediate steps: stop writing to D: to avoid overwriting recoverable data; check whether Volume Shadow Copy/Previous Versions is enabled; restore the most recent backup to a separate folder, not over the live drive; verify file count and a sample file; then copy back. If no shadow copy exists, use file-recovery tools on the external disk only after imaging it; do not install recovery software on D:.
3. Improve the backup plan using only built-in tools and the one spare disk. Include one test that must be performed.
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With one spare disk and built-in tools, aim for versioned copies rather than one weekly mirror: enable Shadow Copies on Archive and Projects for same-day rollback; run a daily Robocopy job to a dated folder on the external disk, keeping at least two generations if space permits; keep the weekly full copy as the baseline. Do not use a mirror-only job, because it copies deletions.
Test quarterly by restoring a sample folder to a test location and comparing file counts and hashes. With only one external disk, the copy is still in the same room, so fire/theft risk remains; record that as a residual risk and rotate the disk offsite when possible. A backup that has never been restored is only a hope, not evidence.