IBM says it is buying Unica, a marketing services company, for $480 million, or $21 per share.

The acquisition brings IBM deeper into the advertising business. In June it agreed to buy Coremetrics Inc., a company that helps target online marketing.

Unica Corp., based in Waltham, Mass., helps companies predict what consumers want and design advertising campaigns based on that information.

IBM expects to close the deal in the fourth quarter. The company's offer of $21 per share is more than double Unica's closing share price Thursday of $9.55.