Kevin Blackwell who has now made his 1st signing since coming to Bramall Lane said:"Because of our problems with injuries i am delighted to bring in John Halls to the club.
"Hopefully, he'll have a good stay and able to put himself in the shop window as he is out of contract at the end of the season."
Halls has had loan spells at Preston and Crystal Palace. He has also played for Stoke City and Arsenal.