CHICAGO (WLS) -- U.S. Homeland Security agents are working to see how deep Russian-linked hackers allegedly tunneled into multiple government computer systems in a newly discovered cyber-attack that apparently went undetected for months. While Russian officials claim to have had nothing to do with infiltrating U.S. government computers, authorities say the Russians targeted some of Americas most sensitive and important computer systems. The Treasury Department and the Commerce Department were both targeted in the intrusion, with a Commerce spokesperson saying "we can confirm there has been a breach in one of our bureaus. We have asked CISA and the FBI to investigate."