You installed the Conduit spyware. To remove it, select Go ▹ Go to Folder… from the Finder menu bar, then copy the following text into the box that opens:
Delete the selected item, if it exists.
Now select Go to Folder… again and enter:
From the folder that opens, delete the following items, if they exist. You may be prompted for your login password.
Close the folder. Now select Go to Folder… again and copy:
Delete that item. Close the Finder windows you opened. Log out and log back in.