1. A host machine for executing a plurality of virtual machines, the host machine comprising: computing hardware, including at least one processor, non-transitory data storage media interfaced with the at least one processor and comprising instructions that, when executed by the at least one processor, cause the computing hardware to implement: the plurality of virtual machines, each one of which provides an isolated execution environment wherein an operating system, a lightweight agent module, and user applications are executed; a special-purpose virtual machine that provides an isolated execution environment in which a central security module is executed; a hypervisor module that coordinates execution of the plurality of virtual machines and the special-purpose virtual machine, wherein information is communicated between each lightweight agent module of each corresponding virtual machine of the plurality of virtual machines and the central security module through the hypervisor module; wherein the central security module performs security-related tasks on behalf of individual ones of the plurality of virtual machines including malware assessment, and includes a malware remediation module configured to generate particularized malware remediation instructions that define actions to be executed by individual ones of the lightweight agent modules of corresponding ones of the plurality of virtual machines in response to an assessment of malware present in any of the virtual machines corresponding to those lightweight agent modules; wherein the lightweight agent module of each of the virtual machines includes an instruction sequence execution module configured to receive and execute the malware remediation instructions; wherein the central security module further includes: a capability assessment module configured to assess a capability of a first instruction sequence execution module of a first lightweight agent module corresponding to a first virtual machine of the plurality of virtual machines to effectively execute the malware remediation instructions; and a security functionality update module configured to provide an advanced security task execution component to be installed in the first virtual machine, in response to an assessment of capability of the first lightweight agent module being insufficient to execute the malware remediation instructions.