Abstract: Systems for processing requests to use virtual computing resources in communicatively isolated computing environments apply a multi-tier framework for limiting the amount of virtual computing resources that can be allocated to a user in a computing environment. A bottom tier is associated with a user account that has not been analyzed for security risks, a top tier is associated with a user account that has been validated to use a corresponding computing environment; an intermediate tier, having limits between the bottom and top tiers, is applied to computing environments where the user has not requested resources. Initially, all computing environments are on the bottom tier. In response to a valid request for resources, validated computing environments are moved to the top tier and all other computing environments are moved to the intermediate tier. Requests in an intermediate-tier computing environment trigger validity review; the computing environment can move to top tier.