Patent ID: 8850573

Claim:
A method comprising: loading, an untrusted executable application code for execution on a computing system, wherein the untrusted executable application code is received from an untrusted source; in response to loading the untrusted executable application code, receiving, at a processor of the computing system, a request to run the untrusted executable application code in the computing system using a reduced level of trust; in response to receiving the request, changing an execution mode of the processor from a first execution mode to a second execution mode; and in response to changing the execution mode from the first execution mode to the second execution mode: modifying, by the processor, an instruction set of the processor to designate one or more instructions that are legal in the first execution mode as being illegal, wherein the modification of the instruction set is performed by using one of a lookup table, a content addressable memory, or an instruction bitmap; and restricting, by the processor, access to memory accessible by the processor in the first execution mode to a subset of the memory, wherein the restriction of the memory is performed using one or more segment tables.