A host-based antimalware client can interface with a server-based antimalware support server. A file is identified at a host device. It is determined whether local reputation data for the file is available at the host device for the file. A query is sent to an antimalware support system relating to the file. Particular reputation data is received from the antimalware support system corresponding to the query. It is determined whether to allow the file to be loaded on the host device based at least in part on the particular reputation data.