Wednesday, September 14, 2016

Script Kitties Early Trick or Treat, Part 1

Some of my old sysadmin tricks became useful again when I analyzed some malware targeting Windows Scripting Host (WSH). In this article I'll share a trick, and in the next, I'll share a treat.

When logic gets hairy, both developers and malware analysts open a debugger to get more information. But what can be done when the target platform is WSH? As it happens, there are debuggers for this, too, and they can be had by installing either Microsoft Office or Microsoft Visual Studio in your dynamic analysis VM. To invoke the debugger, use the /X switch of either cscript.exe or wscript.exe, e.g.:

wscript.exe /X rat3ie.vbs

Here's the Visual Studio debugger, halting on line 1 of a craptacular VBScript RAT:

This gives the ability to view local variables in the Locals tab (at bottom), set breakpoints, and step through code.

That's all for this little nugget. Next time, I'll post a tool I wrote in 2006 that came in handy for conveniently and interactively evaluating VBScript and JScript to de-obfuscate strings and experiment with malware functionality.

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