Explanation
An IS auditor should be concerned because deleting the files logically does not overwrite the files' physical data. Deleting a file from a hard disk only removes the reference or pointer to the file from the file system, but does not erase the actual data stored on the disk sectors. The deleted data can still be recovered using special tools or techniques until it is overwritten by new data. This poses a risk of data leakage, theft, or misuse if the hard disk falls into the wrong hands. To securely dispose of a system containing sensitive data, the hard disk should be wiped or sanitized using methods that overwrite or destroy the physical data beyond recovery.
References:
CISA Review Manual (Digital Version)
CISA Questions, Answers & Explanations Database