The attacks have been ongoing for at least a couple of months and while they're fairly simple in theory, researchers haven't necessarily been able to figure out how the attackers have managed to compromise the domains and get access to the DNS records to add their own sub-domains. What's happened is that attackers have been able to alter the domain records of dozens of existing, legitimate sites, including local government agencies, small businesses, community banks and others and then inserted new sub-domain names into the records.
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