Uncovering the Obfuscation Techniques Used by Malware Authors: A Guide to Identifying and Analyzing UPX1 Pestudio

Introduction:

In recent years, malware authors have employed various techniques to obfuscate their malicious code, making it challenging for security researchers and analysts to identify and analyze them. One such technique is used by the UPX1 Pestudio malware, which employs four distinct methods to conceal its functionality. In this article, we will delve into the world of obfuscation and explore these techniques, providing insights on how to identify and analyze UPX1 Pestudio.

Declaring Unused Functions and Variables:

One common technique used by malware authors is declaring functions and variables that are never being used. This method is designed to confuse analysts and make it difficult for them to understand the code's purpose. In the case of UPX1 Pestudio, this technique is used extensively, making it essential to identify these unused declarations.

Declaring Switch Cases Inside Loops:

Another obfuscation technique employed by UPX1 Pestudio is declaring switch cases inside loops that will only be executed once. This approach is designed to make the code harder to analyze and understand, as it creates complexity and uncertainty about the code's behavior.

Custom-Written Obfuscator:

UPX1 Pestudio uses a custom-written obfuscator to further conceal its functionality. This obfuscator is specifically designed to make it challenging for analysts to identify the malware's purpose and understand how it operates.

Functions Prone to Abuse by Malware Authors:

The AutoIT scripting language provides various functions that can be used by malware authors to perform nefarious tasks. Some of these functions include:

* DllCall()

* DllStructCreate()

* DllStructGetPtr()

* DllCallAddress()

* IsAdmin()

* ObjCreate()

* ObjectGet()

* BinaryToString()

* StringToBinary()

* Binary()

* BinaryLen()

* AutoItSetOption()

* EnvGet()

* Eval()

* Execute()

* InetGet()

* ProcessList()

* RegRead()

* RegWrite()

* FileRead()

* FileWrite()

* ShellExecute()

* ShellExecuteWait()

* Run()

* RunAs()

* Sleep()

* StringReverse()

* TCPSend()

* TCPRecv()

* UDPSend()

* UDPRecv()

Macros Prone to Abuse by Malware Authors:

In addition to the functions mentioned above, AutoIT also provides various macros that can be used by malware authors. Some of these macros include:

* AutoIT documentation for more information on each function and macro.

Analyzing UPX1 Pestudio:

To analyze UPX1 Pestudio, we need to extract the script from the exe file using either Exe2Aut or MyAut2Exe. Once extracted, we can examine the script to identify the obfuscation techniques used. In this case, we see that UPX1 Pestudio is being obfuscated with four distinct methods: declaring unused functions and variables, declaring switch cases inside loops, using a custom-written obfuscator, and compiling the script as an au3 file.

UPX1 Pestudio is just one example of malware that employs various techniques to conceal its functionality. By understanding these obfuscation methods, security researchers and analysts can better identify and analyze such malware, ultimately improving their ability to detect and mitigate malicious code.

Upx1 pestudio