Trusted Information Systems, Inc. (TIS), was a computer security research and development company during the 1980s and 1990s, performing computer and communications (information) security research for organizations such as NSA, DARPA, ARL, AFRL, SPAWAR, and others.

As the company grew, rather than move to Baltimore or the Washington D.C. suburbs, a small office building was constructed on land next to Walker's new home on Route 97.

On a separate path, TIS's primary commercial product, the Gauntlet Firewall, was acquired in 1999 from McAfee by Secure Computing Corporation (SCC), that used to be one of TIS's major competitors, because at the time McAfee wasn't interested in being a firewall vendor.

The end of this product line came in 2013, following McAfee's acquisition of another major firewall vendor, Finland-based Stonesoft.

McAfee announced in October 2013 the intention to migrate their existing installed base of firewalls to Stonesoft's own Stonegate.