The malware used to steal 70 million Target shoppers' data last year wasn't anything all that fancy. It was simply an altered version of an "off-the-shelf" hacker tool called "BlackPOS" — and it apparently was used to infect six other retailers' computer networks, too, a computer security firm reported Friday. According to the firm, IntelCrawler, the malware was created in March 2013, and it is believed to have been used to attack Neiman Marcus' network, too. VISA and top U.S. banks now have detailed information on the tool — but by the time they got it, the tool's author had sold more than 40 versions of the malware to cybercriminal. IntelCrawler's CEO told NBC News that company researchers also figured out that the malware had been installed on at least six other IP addresses, meaning other retailers had been targeted, but his company hadn't yet determined which, or how large they were.

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