Federal contractors that don’t comply with the governmentwide ban on Kaspersky Lab software taking effect today could face a variety of possible punishments and legal headaches.

Complying with the ban in the fiscal 2018 National Defense Authorization Act (Public Law 115-91) is not only very difficult for contractors, but the failure to get their networks “Kaspersky-free” could expose them to terminations, suspensions, or false claims liability, attorneys say.

The government concluded that the Russia-based Kaspersky Lab, which had provided cybersecurity products to defend computer systems in federal agencies, could be used by the Russian government for cyber intrusion.

The cases...