The 31-year-old made over 250 appearances for Leeds before spells with Levante, Sunderland and most recently Blackpool.
Harte, who also made over 75 appearances for the Republic of Ireland, could be in line to make his debut for the Cumbrians against Northampton.
"Ian is a very experienced player and that's probably what we need at the moment," manager Greg Abbott told the Cumbrians' official website.
"We are pleased that he has decided that he wants to roll his sleeves up and help us out with the situation we find ourselves in at the moment.
"He will bring a calmness to the back line and he is another who will help the younger players along. Much of his experience is at the very highest level and that is a very good thing for us to have on board."