1. A computer program product of process access control in an operating system, the computer program product comprising a computer readable storage medium having program instructions embodied therewith, the program instructions executable by a computer to perform a method comprising: receiving, by a kernel and from an agent, a request to execute a first process instance of a first program; obtaining, by the kernel, one or more access control rules related to the agent, wherein the one or more access control rules permit the first process instance to access one or more files or folders, and wherein the one or more access control rules also permit the first process instance to access a third process instance; permitting, by the kernel and based on the one or more access control rules, execution of the first process instance; detecting, by the kernel and during execution of the first process instance, the first process instance attempting to access a second process instance of a second program currently being executed; denying, by the kernel and based on the one or more access control rules, the first process instance permission to access the second process instance; and sandboxing, by the kernel and based on the denied access to the second process instance, the first process instance from the one or more files or folders and the third process instance.