735 ILCS 5/4-126
The sheriff or any other person authorized to serve summons shall, in like manner as summons are served in ordinary civil cases, summon, wherever they may be found in the State, the persons mentioned in such order for attachment as garnishees and all other persons whom the creditor shall designate as having any property, effects, choses in action or credits in their possession or power, belonging to the defendant, or who are in anyway indebted to such defendant, the same as if their names had been inserted in such order for attachment. The persons so summoned shall be considered as garnishees. The return shall state the names of all persons so summoned, and the date of such service on each.
Persons summoned as garnishees shall thereafter hold any property, effects, choses in action or credits in their possession or power belonging to the defendant which are not exempt, subject to the court's order in such proceeding, and shall not pay to the defendant any indebtedness owed to him or her subject to such order, and such property, effects, choses in action, credits and debts shall be considered to have been attached and the plaintiff's claim to have become a lien thereon pending such action.
735 ILCS 5/4-126