Network Access Quarantine Control (NAQC) is a Resource Kit tool in Windows Server 2003 and Windows Server 2008 that allows administrators to prevent remote client computers from connecting to their network with machines that aren't secure.
Once NAQC has been deployed and a remote client connects to the network, a script will be run that determines whether the client computer meets the same security standards as other machines on the network. If the client computer passes, the user is granted access to the rest of the network. If the machine doesn't pass, it's quarantined until the user installs the necessary updates to make it compliant with network policy. The quarantine mode can be configured to automatically apply the necessary updates to bring the client computer into compliance. A timer can be set to drop the connection at a specified interval if the client computer fails to meet the configuration requirements. Once the client computer is in compliance with network policy, the quarantine restrictions are lifted and the standard network policy is applied to the connection.