Iowa Code § 639.11: Bond.

In all cases before it can be issued, the plaintiff must file with the clerk a bond for the use of the defendant, with sureties to be approved by such clerk, in a penalty at least double the value of the property sought to be attached, and in no case less than two hundred fifty dollars conditioned that the plaintiff will pay all damages which the defendant may sustain by reason of the wrongful suing out of the attachment.