(Bloomberg) -- Staples Inc., the largest U.S.office-supply retailer, said 1.16 million payment cards may havebeen affected in a series of data breaches that occurred from Julyinto September.

The theft occurred after criminals deployed malware onpoint-of-sale systems at 115 of Staples’ 1,400 U.S.stores, the Framingham, Massachusetts-based company said today in astatement. The company disclosed in October that it was investigating apotential breach.

Staples is among a growing number of retailers that havehad card systems compromised by hackers. Target Corp. was among thefirst to disclose such an attack, about a year ago, and since thenHome Depot Inc., Sears Holdings Corp.’s Kmart chain and NeimanMarcus Group Ltd. have said they’ve been struck.

Staples shares were little changed at $17.48 at 5:06 p.m.in late trading in New York. The stock had gained 10% this yearthrough the close of regular trading today.

The Staples breach is smaller than the previousincidents at Home Depot and Target. At Home Depot, the world’slargest home-improvement chain, data for 56 million cards and 53million e-mail addresses were compromised. Target’s breach includeddetails for 40 million cards and 70 million addresses, phonenumbers and other information.

Staples is offering free identity protection services and afree credit report to customers who used a payment card at any ofthe affected stores during the relevant time periods.

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