REMnux is a lightweight Linux distribution for assisting malware analysts with reverse-engineering malicious software. The distribution is based on Ubuntu and is maintained by Lenny Zeltser.
In my last blog about Linux Live Environments, I mentioned REMnux, an environment specifically built for malware analysis. I’d spent a little time with REMnux when it first came out, but decided to take the latest version (3.0) for a test drive.
Since I just received the new “Practical Malware Analysis” book from No Starch Press, the detailed lab exercises seemed like a perfect way to test out the tools included in REMnux. While most of the tools in the book are Windows-based, there are Linux-based equivalents found on REMnux.
The first task was downloading the lab files linked from http://practicalmalwareanalysis.com/labs and extracting them.
If you have issues try https://sourceforge.net/projects/labs-encryptzip/ for an encrypted zip download.
WARNING: The lab binaries contain malicious code and you should not install or run these programs without first setting up a safe environment.
Compatibility: The labs are targeted for the Microsoft Windows XP operating system. Many of the labs work on newer versions of Windows, but some of them will not. The labs are designed to mimic realistic malware. Some of them are well-written code that runs reliable and some of them (just like real malware) are poorly written code that may crash, contain memory leaks, or otherwise behave unexpectedly.
Practical Malware Analysis Labs Web Site
My plan to solely use REMnux was immediately thwarted by the self-extracting Windows executable that contained the lab files. There was a EULA (end user license agreement) wrapper as part of the executable that had to be accepted before the files could be extracted — a problem solved with a quick boot of a Windows XP virtual machine. Ideally, the authors will replace or supplement the self-extracting executable with a standard zip file.
After a quick and easy read through the first few chapters, I started to dig into the lab examples using REMnux’s tools. Chapter 1’s labs want you to upload the example binaries to VirusTotal to see whether any antivirus products detect them as possible malware. While I could have used Firefox to upload the files, I chose to use pyew’s “vt” plugin that searches VirusTotal using the MD5 hash of the file instead of uploading the actual file.
Searching just using the MD5 could have backfired if no one had uploaded the file to VirusTotal yet, but given the popularity of the book, the lab files had already been uploaded many times. It doesn’t appear that REMnux currently comes with a command-line tool to upload files to VirusTotal, so here are a couple of options (#1 and #2) that simply require that you get a free API key from VT first.
A few other tasks in the first few “Practical Malware Analysis” labs include looking at executables’ import/export functions, compile date, and packer identification. Pescanner works pretty well to figuring out those answers, but not all of them. For example, pescanner identifies suspicious import functions but does not list them all, and it incorrectly identified some of the executables as having been packed when they weren’t. Pyew faired better by being able to list all imports and exports and correctly identifying the packer, but it did not have an obvious way to show the compile date. But when used together, you can get the exact answers you need.
The last lab in Chapter 1 asks you to use Resource Hacker to look for resources that are stored in the file. To accomplish the same task on Linux, a command-line tool can be used called hachoir-subfile. Running hachoir-subfile against the Lab 1-4 executable will extract the embedded in PE file.
I’m looking forward to digging into the book more and using REMnux further to see just what I can do without having a Windows virtual machine. It’s not that I have anything against Windows — I just like to find alternative Linux-based tools that do the same thing as Windows-based tools. There’s definitely an advantage to having both platforms available for analysis with the plethora of tools to use.
I highly recommend taking a look at the “Practical Malware Analysis” if you’re interested in the topic, as it is one of the best books I’ve seen on subject and the labs are great. I suspect I’ll have more blogs in the future about the book and tools as I spend more time with it and find alternative tools to use for the analysis.
John Sawyer is a Senior Security Analyst with InGuardians. The views and opinions expressed in this blog are his own and do not represent the views and opinions of his employer. He can be reached at johnhsawyer@gmail.com and found on Twitter @johnhsawyer.