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135 lines
6.2 KiB
Markdown
135 lines
6.2 KiB
Markdown
# Common API used in Malware
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## Generic
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### Networking
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| Raw Sockets | WinAPI Sockets |
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| ------------- | -------------- |
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| socket() | WSAStratup() |
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| bind() | bind() |
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| listen() | listen() |
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| accept() | accept() |
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| connect() | connect() |
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| read()/recv() | recv() |
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| write() | send() |
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| shutdown() | WSACleanup() |
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### Persistence
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| Registry | File | Service |
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| ---------------- | ------------- | ---------------------------- |
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| RegCreateKeyEx() | GetTempPath() | OpenSCManager |
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| RegOpenKeyEx() | CopyFile() | CreateService() |
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| RegSetValueEx() | CreateFile() | StartServiceCtrlDispatcher() |
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| RegDeleteKeyEx() | WriteFile() | |
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| RegGetValue() | ReadFile() | |
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### Encryption
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| Name |
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| --------------------- |
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| WinCrypt |
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| CryptAcquireContext() |
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| CryptGenKey() |
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| CryptDeriveKey() |
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| CryptDecrypt() |
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| CryptReleaseContext() |
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### Anti-Analysis/VM
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| Function Name | Assembly Instructions |
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| --------------------------------------------------------- | --------------------- |
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| IsDebuggerPresent() | CPUID() |
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| GetSystemInfo() | IN() |
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| GlobalMemoryStatusEx() | |
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| GetVersion() | |
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| CreateToolhelp32Snapshot \[Check if a process is running] | |
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| CreateFileW/A \[Check if a file exist] | |
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### Stealth
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| Name | |
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| ------------------------ | -------------------------------------------------------------------------- |
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| VirtualAlloc | Alloc memory (packers) |
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| VirtualProtect | Change memory permission (packer giving execution permission to a section) |
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| ReadProcessMemory | Injection into external processes |
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| WriteProcessMemoryA/W | Injection into external processes |
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| NtWriteVirtualMemory | |
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| CreateRemoteThread | DLL/Process injection... |
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| NtUnmapViewOfSection | |
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| QueueUserAPC | |
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| CreateProcessInternalA/W | |
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### Execution
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| Function Name |
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| ---------------- |
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| CreateProcessA/W |
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| ShellExecute |
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| WinExec |
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| ResumeThread |
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| NtResumeThread |
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### Miscellaneous
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* GetAsyncKeyState() -- Key logging
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* SetWindowsHookEx -- Key logging
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* GetForeGroundWindow -- Get running window name (or the website from a browser)
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* LoadLibrary() -- Import library
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* GetProcAddress() -- Import library
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* CreateToolhelp32Snapshot() -- List running processes
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* GetDC() -- Screenshot
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* BitBlt() -- Screenshot
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* InternetOpen(), InternetOpenUrl(), InternetReadFile(), InternetWriteFile() -- Access the Internet
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* FindResource(), LoadResource(), LockResource() -- Access resources of the executable
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## Malware Techniques
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### DLL Injection
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Execute an arbitrary DLL inside another process
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1. Locate the process to inject the malicious DLL: CreateToolhelp32Snapshot, Process32First, Process32Next
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2. Open the process: GetModuleHandle, GetProcAddress, OpenProcess
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3. Write the path to the DLL inside the process: VirtualAllocEx, WriteProcessMemory
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4. Create a thread in the process that will load the malicious DLL: CreateRemoteThread, LoadLibrary
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Other functions to use: NTCreateThreadEx, RtlCreateUserThread
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### Reflective DLL Injection
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Load a malicious DLL without calling normal Windows API calls.\
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The DLL is mapped inside a process, it will resolve the import addresses, fix the relocations and call the DllMain function.
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### Thread Hijacking
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Find a thread from a process and make it load a malicious DLL
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1. Find a target thread: CreateToolhelp32Snapshot, Thread32First, Thread32Next
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2. Open the thread: OpenThread
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3. Suspend the thread: SuspendThread
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4. Write the path to the malicious DLL inside the victim process: VirtualAllocEx, WriteProcessMemory
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5. Resume the thread loading the library: ResumeThread
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### PE Injection
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Portable Execution Injection: The executable will be written in the memory of the victim process and it will be executed from there.
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### Process Hollowing
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The malware will unmap the legitimate code from memory of the process and load a malicious binary
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1. Create a new process: CreateProcess
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2. Unmap the memory: ZwUnmapViewOfSection, NtUnmapViewOfSection
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3. Write the malicious binary in the process memory: VirtualAllocEc, WriteProcessMemory
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4. Set the entrypoint and execute: SetThreadContext, ResumeThread
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## Hooking
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* The **SSDT** (**System Service Descriptor Table**) points to kernel functions (ntoskrnl.exe) or GUI driver (win32k.sys) so user processes can call these functions.
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* A rootkit may modify these pointer to addresses that he controls
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* **IRP** (**I/O Request Packets**) transmit pieces of data from one component to another. Almost everything in the kernel uses IRPs and each device object has its own function table that can be hooked: DKOM (Direct Kernel Object Manipulation)
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* The **IAT** (**Import Address Table**) is useful to resolve dependencies. It's possible to hook this table in order to hijack the code that will be called.
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* **EAT** (**Export Address Table**) Hooks. This hooks can be done from **userland**. The goal is to hook exported functions by DLLs.
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* **Inline Hooks**: This type are difficult to achieve. This involve modifying the code of the functions itself. Maybe by putting a jump at the begging of this.
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