DrSemu : Malware Detection & Classification Tool Based on Dynamic Behavior

DrSemu is a malware Detection and Classification Tool Based on Dynamic Behavior.

It runs executables in an isolated environment, monitors the behavior of a process, and based on Dr.Semu rules created by you or the community, detects if the process is malicious or not.

With Dr.Semu you can create rules to detect malware based on dynamic behavior of a process.

Isolation through redirection

Everything happens from the user-mode. Windows Projected File System (ProjFS) is used to provide a virtual file system. For Registry redirection, it clones all Registry hives to a new location and redirects all Registry accesses.

See the source code for more about other redirections (process/objects isolation, etc).

Also Read – Fuzzowski : The Network Protocol Fuzzer

Monitoring

Dr.Semu uses DynamoRIO (Dynamic Instrumentation Tool Platform) to intercept a thread when it’s about to cross the user-kernel line.

It has the same effect as hooking SSDT but from the user-mode and without hooking anything.

At this phase, Dr.Semu produces a JSON file, which contains information from the interception.

Detection

After terminating the process, based on Dr.Semu rules we receive if the executable is detected as malware or not.

Dr.Semu rules

They are written in Python or LUA (located under dr_rules) and use dynamic information from the interception and static information about the sample. It’s trivial to add support of other languages.

Example (Python): https://gist.github.com/secrary/ac89321b8a7bde998a6e3139be49eb72

Example (Lua): https://gist.github.com/secrary/e16daf698d466136229dc417d7dbcfa3

Usage

  • Use PowerShell to enable ProjFS in an elevated PowerShell window:

Enable-WindowsOptionalFeature -Online -FeatureName Client-ProjFS -NoRestart

DrSemu.exe –target file_path

DrSemu.exe –target files_directory

DEMO

BUILD

  • Use PowerShell to enable ProjFS in an elevated PowerShell window:

Enable-WindowsOptionalFeature -Online -FeatureName Client-ProjFS -NoRestart

  • Install Python 3 x64
  • Download DynamoRIO and extract into bin folder and rename to dynamorio
  • Build pe-parser-library.lib library:
    • Generate VS project from DrSemu\shared_libs\pe_parse using cmake-gui
    • Build 32-bit library under build (\shared_libs\pe_parse\build\pe-parser-library\Release\) and 64-bit one under build64
    • Change run-time library option to Multi-threaded (/MT)
  • Set LauncherCLI As StartUp Project

Limitations

  • Minimum supported Windows version: Windows 10, version 1809 (due to Windows Projected File System)
  • Maximum supported Windows version: Windows 10, version 1809 (DynamoRIO supports Windows 10 versions until 1809)
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