The nation's cybersecurity agency warned of a “grave” risk to government and private networks. The hack compromised federal agencies and “critical infrastructure” in a sophisticated attack that was hard to detect and will be difficult to undo, the Cybersecurity and Infrastructure Security Agency said in an unusual warning message Thursday. CISA officials did not respond to questions and so it was unclear what the agency meant by a “grave threat” or by “critical infrastructure” possibly targeted in the attack that the agency says appeared to have begun last March. The agency previously said the perpetrators had used network management software from Texas-based SolarWinds t o infiltrate computer networks. Members of Congress said they feared that taxpayers’ personal information could have been exposed because the IRS is part of Treasury, which used SolarWinds software.

But President Donald Trump, long wary of blaming Moscow for cyberattacks has so far been silent. But President Donald Trump, long wary of blaming Moscow for cyberattacks, has been silent. Speaking to reporters Friday, Trump economic adviser Larry Kudlow did not commit to blaming the Kremlin, saying, “People are saying Russia. The Trump administration and Western allies similarly expelled diplomats over Moscow's alleged poisoning of an ex-intelligence officer in Britain. Exposing Kremlin corruption, including how Russian President Vladimir Putin accrues and hides his wealth, may amount to even more formidable retaliation.