KnowWho is a data content and services provider of contact and profile information for federal, state, and local government officials. KnowWho has no self-service opt-out tool; it references a "request form" without linking to one, so in practice you email privacyandsecurity@knowwho.com (or info@knowwho.com / call 1-888-566-9946) to request access, deletion, or a marketing/sale opt-out. They say they will take reasonable steps to verify your identity, and they give no specific response deadline beyond "the time period stated by applicable law."