The holiday data breach at Target Corp. appeared to be part of a broad and highly sophisticated international hacking campaign against multiple retailers, according to a report prepared by federal and private investigators that was sent to financial-services companies and retailers.

The report offers some of the first details to emerge about the source of the attack that compromised 40 million credit- and debit-card accounts and personal data for 70 million people. It also provided further evidence the attack on Target during...