The United States government has sent a confidential, 16-page document to major retailers that outlines how hackers infiltrated Target's data systems late last year and made off with sensitive information belonging to over 70 million customers. As the investigation into that breach continues, the government is sharing some of what it's learned so far. According to CNBC, the report reveals that the malware which infected Target was "partly written in Russian" and that the perpetrators "displayed innovation" and "a high degree of skill."

The bulletin tells merchants how they can identify the methods and malicious software used in the attack, Reuters says, which Target's anti-virus tools ultimately failed to pick up on. Little else is known about what the document contains, though it's length suggests the Secret Service and Justice Department are making some headway in their investigation of the incident. Of course, the biggest challenge of all is finding those responsible; no arrests linked to the breach have been publicly reported.