Mwemu
x86 malware emulator
Install / Use
/learn @sha0coder/MwemuREADME
MWEmu
Official documentation
What is this?
It's a hardware emulator + OS process simulator implemented in pure rust.
This approach is very convenient to malware analysis and other stuff (PE, shellcode etc)
The OS is mainly windows, it emulates a windows process, some very basic support for linux.
The hardware is x86 32/64bits it's fast and reliable.
Three ways of using the software
- mwemu commandline https://github.com/sha0coder/mwemu
- libmwemu crate https://crates.io/crates/libmwemu
- pymwemu https://pypi.org/project/pymwemu/
note about scemu
The project was renamed from scemu to mwemu.
Some Videos
r2con2025 using radare2 from mwemu for doing static analisys and visualization inside an emulation moment.
Features
- 📦 rust safety, good for emulating malware.
- All dependencies are in rust.
- ⚡ very fast emulation (much faster than unicorn)
- benchmarks
- 25,767,432 instructions/second
- 680,000 instructions/second printing every instruction -vv.
- powered by iced-x86 rust dissasembler awesome library.
- commandline tool, rust library, and python library.
- iteration detector.
- memory and register tracking.
- colorized.
- stop at specific moment and explore the state or modify it.
- 339 CPU instructions implemented.
- 260 winapi 32bits implemented of 15 dlls.
- 204 winapi 64bits implemented of 10 dlls.
- all linux syscalls.
- SEH chains.
- vectored exception handler.
- PEB, TEB structures.
- dynamic linking.
- IAT binding.
- delay loading.
- memory allocator.
- react with int3.
- non debugged cpuid.
- 32bits and 64bits shellcode emulation.
- pe32 and pe64 executables emulation.
- fully emulation with known payloads:
- metasploit shellcodes.
- metasploit encoders.
- cobalt strike.
- shellgen.
- guloader (not totally for now, but arrive further than the debugger)
- mars stealer pe32.
- bumblebee.
- partial emulation with complex malware functions:
- guloader
- xloader
- danabot
pymwemu vs malware
- raccoon, strings decryption
- vidar, strings decryption
- xloader, total decrypt, keygen, build url encryption.
- lokibot, api deobfuscation
- mars unpacking and getting ioc
- shikata decoding and getting ioc
- danabot strings decryption
- zloader strings decryption
- bumblebee unpacking after emulating 25,515,274,634 instructions.
- enigma loader api deobuscation and drop decryption
- bugsleep unpack
- gozi bss decrypt and dga predictor.
Capture an emulation moment
During the emulation you can see the numer of cpu insturctions emulated, that's an unique ID for an emulation moment.
With -c flag you stop the emulation in a specific moment and inspect what is going on with the console.
Usage
MWEMU emulator for malware 0.7.11
@sha0coder
USAGE:
mwemu [FLAGS] [OPTIONS]
FLAGS:
-6, --64bits enable 64bits architecture emulation
--banzai skip unimplemented instructions, and keep up emulating what can be emulated
--flags trace the flags hex value in every instruction.
-F, --fpu trace the fpu states.
-h, --handle handle Ctrl+C to spawn console
--help Prints help information
-l, --loops show loop interations, it is slow.
-m, --memory trace all the memory accesses read and write.
-n, --nocolors print without colors for redirectin to a file >out
-r, --regs print the register values in every step.
-p, --stack_trace trace stack on push/pop
-t, --test test mode
--version Prints version information
-v, --verbose -vv for view the assembly, -v only messages, without verbose only see the api calls and goes
faster
OPTIONS:
-A, --args <ARGS> provide arguments to the EXE like: --args '"aa" "bb"'
--cmd <COMMAND> launch a console command
-b, --base <ADDRESS> set base address for code
-c, --console <NUMBER> select in which moment will spawn the console to inspect.
-C, --console_addr <ADDRESS> spawn console on first eip = address
-d, --dump <FILE> load from dump.
-a, --entry <ADDRESS> entry point of the shellcode, by default starts from the beginning.
-e, --exit <POSITION> exit position of the shellcode
-f, --filename <FILE> set the shellcode binary file.
-i, --inspect <DIRECTION> monitor memory like: -i 'dword ptr [ebp + 0x24]
-L, --log <LOG_FILENAME> log output to file
-M, --maps <PATH> select the memory maps folder
--mxcsr <MXCSR> set mxcsr register
--r10 <R10> set r10 register
--r11 <R11> set r11 register
--r12 <R12> set r12 register
--r13 <R13> set r13 register
--r14 <R14> set r14 register
--r15 <R15> set r15 register
--r8 <R8> set r8 register
--r9 <R9> set r9 register
--rax <RAX> set rax register
--rbp <RBP> set rbp register
--rbx <RBX> set rbx register
--rcx <RCX> set rcx register
--rdi <RDI> set rdi register
--rdx <RDX> set rdx register
-R, --reg <REGISTER1,REGISTER2> trace a specific register in every step, value and content
--rflags <RFLAGS> set rflags register
--rsi <RSI> set rsi register
--rsp <RSP> set rsp register
-x, --script <SCRIPT> launch an emulation script, see scripts_examples folder
--stack_address <ADDRESS> set stack address
-s, --string <ADDRESS> monitor string on a specific address
-T, --trace <TRACE_FILENAME> output trace to specified file
-S, --trace_start <TRACE_START> start trace at specified position
-V, --verbose_at <NUMBER> start displaying assembly at specific position (is like -vv enabled in specific
moment)
Command line examples
64bits needs the -6 flag, -vv for viewing asm, and -c for spawning console at specific moment:
cargo run --release -- -f /tmp/shellcode.bin -6 -vv -c 19291
Testing
make tests
Some use cases
mwemu emulates a simple shellcode detecting the execve() interrupt.
note that I renamed this tool from scemu to mwemu (in italian scemu is a bad word)
We select the line to stop and inspect the memory.
After emulating near 2 million instructions of GuLoader win32 in linux, faking cpuid's and other tricks in the way, arrives to a sigtrap to confuse debuggers.
Example of memory dump on the api loader.
There are several maps by default, and can be created more with apis like LoadLibraryA or manually from the console.
Emulating basic windows shellcode based on LdrLoadDLl() that prints a message:
The console allow to view an edit the current state of the cpu:
--- console ---
=>h
--- help ---
q ...................... quit
cls .................... clear screen
h ...................... help
s ...................... stack
v ...................... vars
r ...................... register show all
r reg .................. show reg
rc ..................... register change
f ...................... show all flags
fc ..................... clear all flags
fz ..................... toggle flag zero
fs ..................... toggle flag sign
c ...................... continue
ba ..................... breakpoint on address
bi ..................... breakpoint on instruction number
bmr .................... breakpoint on read memory
bmw .................... breakpoint on write memory
bc ..................... clear breakpoint
n ...................... next instruction
eip .................... change eip
push ................... push dword to the stack
pop .................... pop dword from stack
fpu .................... fpu view
md5 .................... check the md5 of a memory map
seh .................... view SEH
veh .................... view vectored execption pointer
m ...................... memory maps
ma ..................... memory allocs
mc ..................... memory create map
mn ..................... memory name of an address
ml ..................... memory load file content to map
mr ..................... memory read, speficy ie: dword ptr [esi]
mw ..................... memory read, speficy ie: dword ptr [esi] and then: 1af
md ..................... memory dump
mrd .................... memory read dwords
mds .................... memory dump str
