Tactical to Functional

This note is based on an excellent blog series by Jared Atkinson and explores the ways we can and should go deeper than the Tactics, Techniques & Procedures.

Taxonomy

• Functions, both documented and undocumented, of the Win API and syscalls
  • e.g.: ntdll.dll's NtQuerySystemInformation
  • e.g.: kernel32.dll's OpenProcess
  • e.g.: kernel32.dll's ReadProcessMemory
  • e.g.: syscall NtOpenProcess
• Compound Functions are individual functions that perform multiple operations
  • e.g.: kernel32.dll's Toolhelp32ReadProcessMemory which performs Process Access and Process Read
• Operations work as a container for teleologically equivalent functions
• Synonyms
  • Functional Synonyms are tools which rely on the exact same function calls to achieve their outcome.
  • Procedural Synonyms are tools which sequence the same operations in the same order as each other, but use differing functions or sequence them differently.
  • Sub-Technical Synonyms are tools that differ at the procedural level, but still implement the same sub-technique.

Method

1. Understand the source code of the different implementations of the technique/sub-technique and enumerate the functions used. → Capability Abstraction

   

2. Understand that there are alternatives to these functions and that a single function can have multiple purposes (Compound Functions). So abstract the individual functions into what purpose(s) they serve, aka. Operations.

   

3. Consider that there are alternative Operation Paths (e.g.: instead of accessing a process, maybe we can clone it and access that), so enumerate these as well.

4. Now search for all possible, also the undocumented, functions that implement the operations in the different Operation Paths.

   

What Exactly Do We Define as a Procedure?

A procedure is "a sequence of operations that, when combined, implement a technique or sub-technique."

The procedures are the pattern of steps to execute, not the execution of the steps. E.g.:

1. Enumerate processes to obtain the process identifier for lsass.exe.
2. Open a handle to lsass.exe with the PROCESS_VM_READ access right.
3. Read the memory of lsass.exe to obtain the credentials stored within.

The vital point here is not the steps; it is what the steps represent. Each step corresponds with an operation:

• Step 1 == Process Enumerate
• Step 2 == Process Access
• Step 3 == Process Read

The steps define a sequence of operations that implements a sub-technique, specifically, the sequence of operations that is instantiated by Mimikatz's sekurlsa::logonPasswords command.

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Relevant Note(s): Capability Abstraction