Securely Deleting Encrypted Data on Linux

15 minutes
  • 5 Learning Objectives

About this Hands-on Lab

In this scenario you are the Systems Administrator for a healthcare company. Your manager has tasked you with logging into the fileserver running CentOS Linux 7.7 and securely deleting some sensitive patient data, ensuring that it cannot be easily recovered. No other files should be altered.

Learning Objectives

Successfully complete this lab by achieving the following learning objectives:

Confirm File Is Readable

Confirm the size and permissions of the file:

[cloud_user@$host]$ sudo ls -l /mnt/patient.1

Show the contents of the file:

[cloud_user@$host]$ sudo cat /mnt/patient.1
Fill Free Space

Be sure to double check the path, as this command does no error checking and will overwrite data:

[cloud_user@$host]$ sudo dd if=/dev/urandom of=/mnt/junk status=progress; sync
Overwrite File

The shred command is the simplest method. Specifying -x ensures that the filesize remains unchanged:

[cloud_user@$host]$ sudo shred -x /mnt/patient.1

If the shred command is not available, we can use the following dd command:

[cloud_user@$host]$ sudo dd if=/dev/urandom of=/mnt/patient.1 bs=45 count=1 iflag=fullblock status=progress
Confirm File Was Overwritten and Remove

Show file contents:

[cloud_user@$host]$ sudo cat /mnt/patient.1

Remove file:

[cloud_user@$host]$ sudo rm /mnt/patient.1
Restore Free Space

Remove junk file:

[cloud_user@$host]$ sudo rm /mnt/junk

Additional Resources

In this scenario you are the Systems Administrator for a healthcare company. Your manager has tasked you with logging into the fileserver running CentOS Linux 7.7 and securely deleting some sensitive patient data, ensuring that it cannot be easily recovered. No other files should be altered.

This patient data exists in /mnt/patient.1. To ensure it is securely deleted, perform the following steps:

  1. Confirm the current patient file is readable.
  2. Fill any free space on the volume to eliminate any file remnants.
  3. Overwrite patient file with random data.
  4. Confirm file was overwritten and remove.
  5. Restore free space.

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