HOW TO MAKE COBALT STRIKE BEACON STEALTHY CODE
You need to direct the code flow to that memory region.You need to get your shellcode into that address space.You need virtual address space that is marked as executable (otherwise DEP will throw an exception).In order to execute your shellcode you need to complete the following three checks: Dynamically Allocate MemoryĪfter defining the basics, let’s have a look on what is needed to execute shellcode within your process memory space. If you initialize a variable locally within a function, this variable will be placed on the STACK.
STACK: The stack is the place every static local variable is assigned to.
Every time you create an object for which the space that is needed is determined at run time, the required address space is dynamically assigned within the HEAP (usually using alloc() or similar system calls). HEAP: This is where all your dynamic local variables are stored. DATA segment, this section holds any uninitialized global or static variables. Any variable that is not bound to a specific function is stored here. DATA section contains globally initialized or static variables. In this area you will find the main entry of the executable, where the execution flow starts. TEXT Segment: This is where the executable process image is placed. Most of these sections should be familiar, but to keep everyone on the same page, here is a quick rundown of these sections: The representation above shows what the global virtual address space looks like, let’s break this down for a single process:Ī single processes virtual memory space consists of multiple sections that are placed somewhere within the available space boundaries by Address Space Layout Randomization (ASLR). Please note the latter is only true for environments without Virtualization-based Security (VBS), but that’s a different topic. The first takeaway from this is that each process gets its own, private virtual address space, where the “kernel space” is kind of a “shared environment”, meaning each kernel process can read/write to virtual memory anywhere it wants to. This visual representation is based on Microsoft’s description given here. The first concept that needs to be understood is that the entire virtual memory space is split into two relevant parts: Virtual memory space reserved for user processes (user space) and virtual memory space reserved for system processes (kernel space), as shown below: In essence the following four execution techniques will be covered:Įspecially the first two techniques are very widely known and most should be familiar with these, however, the latter two might be new to some.Įach of these techniques describes a way of executing code in a different memory section, therefore it is necessary to review a processes memory layout as a first step.
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