Why does the help desk want your password?

While at work, you receive a call from Brian from the company help desk in New York. Brian informs you that during the backup process last night, your user account was apparently damaged during the file transfer. To resolve the issue, Brian asks for your username and password so he can login and recover the damaged files. What kind of security problem is this?

A) Security patch

B) Malicious software

C) Spyware

D) Social engineering