frida-wshook is an analysis and instrumentation tool which uses frida.re to hook common functions often used by malicious script files which are run using WScript/CScript.
The tool intercepts Windows API functions and doesn't implement function stubs or proxies within the targeted scripting language. This allows it to support analyzing a few different script types such as:
- .js (JScript)
- .vbs (VBScript)
- .wsf (WSFile) (Initial support/testing. - Does not support specific jobs)
By default script files are run using cscript.exe and will output:
- COM ProjIds
- DNS Requests
- Shell Commands
- Network Requests
Warning!!! Ensure that you run any malicious scripts on a dedicated analysis system. Ideally, a VM with snapshots so you can revert if a script gets away from you and you need to reset the system.
Although common methods have been hooked, Windows provides numerous APIs which allow developers to interact with a network, file system and execute commands. So it is entirely possible to encounter scripts leveraging uncommon APIs for these functions.
Install & Setup
- Install Python 2.7
- Install the Frida python bindings using pip
pip install frida- Clone (or download) the frida-wshook repository.
Supported OS
frida-wshook has been tested on Windows 10 and Windows 7 and should work on any Windows 7 + environment. On x64 systems CScript is loaded from the C:\Windows\SysWow64 directory.
It may work on WindowsXP, but I suspect that CScript may use the legacy API calls and would bypass the instrumentation.
Usage
The script supports a number of optional commandline arguments that allow you to control what APIs the scripting host can call.
usage: frida-wshook.py [-h] [--debug] [--disable_dns] [--disable_com_init]
[--enable_shell] [--disable_net]
script
frida-wshook.py your friendly WSH Hooker
positional arguments:
script Path to target .js/.vbs file
optional arguments:
-h, --help show this help message and exit
--debug Output debug info
--disable_dns Disable DNS Requests
--disable_com_init Disable COM Object Id Lookup
--enable_shell Enable Shell Commands
--disable_net Disable Network Requestspython wshook.py bad.jspython wshook.py --debug bad.jspython frida-wshook.py --enable_shell bad.vbspython frida-wshook.py --disable_net bad.vbspython frida-wshook.py --disable_com_init bad.vbsHooked Functions
- ole32.dll
- Shell32.dll
- Ws2_32.dll
Known Issues
- Network responses are not captured
- Disabling Object Lookup can cause the script to only output the first ProgId...Malware QA can be lacking.
- WSF files with a specific job to target currently isn't supported
TODO
- Change GetAddrInfoExW to use .replace instead of .attach
- Add additional tracing and hooks to cover more APIs
- Look at bypassing common anti-analysis techniques found in scripts (sleeps etc)
- Update and improve network request hooking (ie: currently it captures requests, but not responses)
Feedback / Help
Any questions, comments or requests you can find us on twitter: @seanmw or @herrcore