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Unconventional Training Club

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Samuel Thomas
Samuel Thomas

Remote Load Library And Detour Injecting

This technique is one of the most common techniques used to inject malware into another process. The malware writes the path to its malicious dynamic-link library (DLL) in the virtual address space of another process, and ensures the remote process loads it by creating a remote thread in the target process.

remote load library and detour injecting

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Malware can insert the location of their malicious library under the Appinit_Dlls registry key to have another process load their library. Every library under this registry key is loaded into every process that loads User32.dll. User32.dll is a very common library used for storing graphical elements such as dialog boxes. Thus, when a malware modifies this subkey, the majority of processes will load the malicious library. Figure 6 demonstrates the trojan Ginwui relying on this approach for injection and persistence. It simply opens the Appinit_Dlls registry key by calling RegCreateKeyEx, and modifies its values by calling RegSetValueEx.

In this post, I covered ten different techniques that malware uses to hide its activity in another process. In general, malware either directly injects its shellcode into another process or it forces another process to load its malicious library. In Table 1, I have classified the various techniques and provided samples to serve as a reference for observing each injection technique covered in this post. The figures included throughout the post will help the researcher recognize the various techniques when reversing malware.

EasyHook is a library that allows you to hook unmanaged code with pure managed functions from within a fully managed environment on 32-bit and 64-bit Windows versions. EasyHook supports injecting assemblies built for .NET Framework 3.5 and 4.0 and can also inject native DLLs. The library is distributed under the MIT license.

To start using the library, we must create the NativeInjectionEntryPoint function in our DLL. For remote native/unmanaged hooks, EasyHook is expecting to find the NativeInjectionEntryPoint export method within our DLL. EasyHook will call this method once the DLL has been successfully injected.

The third technique which is fairly frequently applied involves loading a second copy of a DLL which has been hooked into memory using LoadLibrary and then calling the required API as implemented by the copy of the DLL rather than the original. Following with the process creation example, using this technique a copy of the ntdll.dll file would be stored somewhere on disk (such as within the Windows temporary folder) and this copy would then be loaded as a library. GetProcAddress would then be used to locate the functions of interest within the DLL copy:

The above code utilises the VirtualAllocEx and WriteProcessMemory functions to inject an executable payload (stored in rgbPayload into the remote process), and then creates and tasks a remote thread with an APC (via CreateRemoteThread and QueueUserAPC), and finally releases the thread enabling it to wake and execute any queued APCs using NtAlertResumeThread before promptly terminating.

The first is that FireWalker can slow performance as executing the TrapFilter function before each instruction decreases the performance of traced code by many orders of magnitude. The performance penalty could be accepted for tasks which are infrequently performed such as process creation, remote process memory manipulation and thread creation, etc. but in general terms it is too slow to be used for every function call and would need to be used sparingly. It will however likely be negligible for suspicious functions inside general purpose red team tools such as loaders, initial access payloads and implants.

However, we did detect a recent use of the same bypass that connected to a remote server to obtain a PowerShell-based malware downloader. This one appears to have been part of a Proxy Logon-based attack that attempted to load a Meterpreter backdoor DLL from a server in Russia:

While manipulation of the properties of the AmsiUtils interface is still a common method of attempting AMSI bypass, over 98 percent of the bypass attempts we see in recent telemetry focus on a different approach: tampering with the code of the AMSI library itsef. already loaded into memory to make scan requests fail. In this attack, the malware locates the library AmsiScanBuffer in memory, and then overwrites the instructions at that address with new ones that redirect to an error message. An implementation of this attack in PowerShell, unobfuscated, would look like this:

The memory patch technique has been integrated into the commercial offensive security platform Cobalt Strike as an option called amsi_disable. It has also been seen in a number of malware families, including in a downloader for the Agent Tesla remote access tool (RAT) malware we recently analyzed, in WannaMine crypto-jacking malware installations, and in recent ProxyLogon-based intrusions dropping PowerShell-based RATs.

Import Address Table(IAT): Address table is used as a lookup table when the application is calling a function in a different module. It can be in the form of both import by ordinal and import by name. Because a compiled program cannot know the memory location of the libraries it depends upon, an indirect jump is required whenever an API call is made. As the dynamic linker loads modules and joins them together, it writes actual addresses into the IAT slots, so that they point to the memory locations of the corresponding library functions.

After assembling the shellcode with nasm -f bin TerminateProcessHook.asm command, a simple shellcode injector program is used for executing the payload inside the task manager application. There are many different methods for injecting the shellcode into a running process such as using powersploit , empire or metasploit it is just a matter of choice. Running such injection on a continuous loop may be used to prevent premature termination of your infiltration software against user-land analysis and management tools.

Malware loaders are essentially remote access trojans (RATs) that establish communication between the attacker and the compromised system. Loaders typically represent the first stage of a compromise. Their primary goal is to download and execute additional payloads, from the attacker-controlled server, on the compromised system without detection.

After obtaining the addresses to memory pages of the detour functions for hooking, the loader uses function VirtualProtect to change the memory permissions of the target pages. After changing the permissions, the loader writes the in-line hooks in sub_180002978. Then VirtualProtect is called again to restore the page permissions.

The final function executed by the loader is sub_1800013A0. The malware uses the function LoadLibraryW to load the DLL module. It then uses the function GetProcAddress to obtain the address of a specific function exported by the library loaded.

The detour function at 0x180001D4C is used to hook function NtMapViewOfSection, which lays the groundwork for hollowing the loaded module (in this case, gdiplus.dll) with the unpacked Bumblebee binary. The detour function is capable of the following actions:

After creating a section object, the detour function calls NtMapViewOfSection, via a pointer. Now the view for the section is created by the system. The function sub_180002E74 is responsible for filling the mapped view with an unpacked payload.

rpath designates the run-time search path hard-coded in an executable file or library. Dynamic linking loaders use the rpath to find required libraries. Specifically it encodes a path to shared libraries into the header of an executable (or another shared library). This RPATH header value (so named in the Executable and Linkable Format header standards) may either override or supplement the system default dynamic linking search paths.

Some of the keys explained in the following are defined in the library arrows.meta, others are always available. This has to do with the question of whether the arrow key needs to be supported directly in the pgf core or not. In general, the following explanations assume that arrows.meta has been loaded.

\usetikzlibrarybending % LaTeX and plain TeX \usetikzlibrary[bending] % ConTeXt Load this library to use the flex, flex', or bending arrow keys. When this library is loaded, flex becomes the default mode that is used with all paths, unless quick is explicitly selected for the arrow tip.

By default, > is a shorthand for To and To is a shorthand for to (an arrow from the old libraries) when arrows.meta is not loaded library. When arrows.meta is loaded, To is redefined to mean the same as Computer Modern Rightarrow.

The only reason this library is not loaded by default is for compatibility with older versions of TikZ. You can, however, safely load and use this library alongside the older libraries arrows and arrows.spaced.

Manipulating maximum segment size and selective acknowledgement (SACK) may be used by a remote peer to cause a denial of service by an integer overflow in the Linux kernel, potentially causing a Kernel panic.[84] Jonathan Looney discovered cite.citationfont-style:inherit; .citation qquotes:"\"""\"""'""'".mw-parser-output .citation:targetbackground-color:rgba(0,127,255,0.133).mw-parser-output .id-lock-free a,.mw-parser-output .citation .cs1-lock-free abackground:url("//")right 0.1em center/9px .id-lock-limited a,.mw-parser-output .id-lock-registration a,.mw-parser-output .citation .cs1-lock-limited a,.mw-parser-output .citation .cs1-lock-registration abackground:url("//")right 0.1em center/9px .id-lock-subscription a,.mw-parser-output .citation .cs1-lock-subscription abackground:url("//")right 0.1em center/9px .cs1-ws-icon abackground:url("//")right 0.1em center/12px .cs1-codecolor:inherit;background:inherit;border:none; .cs1-hidden-errordisplay:none; .cs1-maintdisplay:none;color:#3a3; .citation .mw-selflinkfont-weight:inherit2019-11477, CVE-2019-11478, CVE-2019-11479 on June 17, 2019.[85]


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