Theme Overview

Our last release looked at APT40 targeting the government organizations with watering-hole and password reuse attacks.

For this week’s TTP Tuesday we are releasing a new APT40 themed chain based on defense evasion techniques. We’ll be looking at a process injection technique and the user of native API calls to perform several defense evasion and discovery techniques.

Shellcode Injection

Process injection is method of code execution that typically abuses legitimate OS functionality, such as the loading of a shared library. On a Windows system, these shared libraries are called DLLs and they contain, in addition to useful exported functions, some boilerplate structure that helps Windows load and use the DLL.

Shellcode is typically a small piece of position independent assembly code. Since it doesn’t contain all the boilerplate found in a shared library, it’s an overall much smaller payload. Shellcode injection, itself a process injection technique, simply loads shellcode into a target process’s memory and executes it.

With APT40, some of their malware has been observed using process injection and shellcode injection to load malware into a target process. For this week’s release we’re using Sliver to demonstrate shellcode injection on a Windows host. The included shellcode launches calc.exe on any x64 Windows machine. To run your own shellcode, just replace the shellcode payload in the TTP and you’re all set!

Native API

Shell bad.

Commands executed through a shell, like PowerShell and Bash, are easy to detect. In addition to logging, defenders often have detection capabilities to alert on or block shell commands. The alternative to shell execution, which most modern C2 frameworks use in their agents, is the use of native operating system API calls or shared libraries (such as the C library) to perform various actions.

Sliver agents, available through Operator’s Sliver plugin, contain several native API capabilities. For this release, we’ve implemented a dozen or so for use in Operator that you can modify and mix into your own chains.

To date, we now support the following Sliver commands through the use of executors:

• registrycreatekey

• registryread

• registrydeletekey

• execute-shellcode

• execute-assembly

• registerextension (register a COFF loader)

• bof (load a Beacon Object File)

• ifconfig

• netstat

• pwd

• ls

• mkdir

• rm

• ps

• terminate

• getprivs

Back in the workshop, we’re building new agents that include these executors (and more!) to replace our current flagship agents. Expect better stealth and greater execution options in our upcoming releases.

Thanks for reading! We’ll be back next week with more examples of APT40 tradecraft!

Check it out on the Prelude chains website.

Watch a demonstration:

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