MADBURY, N.H. — The Kremlin hacked our presidential election, is waging a cyberwar against our NATO allies and is probing opportunities to use similar tactics against democracies worldwide. Why then are federal agencies, local and state governments and millions of Americans unwittingly inviting this threat into their cyber networks and secure spaces?

That threat is posed by antivirus and security software products created by Kaspersky Lab, a Moscow-based company with extensive ties to Russian intelligence. To close this alarming national security vulnerability, I am advancing bipartisan legislation to prohibit the federal government from using Kaspersky Lab software.

Kaspersky Lab insists that it has “no inappropriate ties with any government.” The company’s products, which are readily available at big-box American retailers, have more than 400 million users around the globe. And it provides security services to major government agencies, including the Department of State, the National Institutes of Health and, reportedly, the Department of Defense.

But at a public hearing of the Senate Intelligence Committee in May, six top intelligence officials, including the heads of the F.B.I., C.I.A. and National Security Agency, were asked if they would be comfortable with Kaspersky Lab software on their agencies’ computers. Each answered with an unequivocal no. I cannot disclose the classified assessments that prompted the intelligence chiefs’ response. But it is unacceptable to ignore questions about Kaspersky Lab because the answers are shielded in classified materials. Fortunately, there is ample publicly available information to help Americans understand the reasons Congress has serious doubts about the company.