Frank Block

I’m happy to announce the publication of the paper Windows memory forensics: Identification of (malicious) modifications in memory-mapped image files at this years DFRWS USA, and the release of the corresponding volatility plugin. With this research came also an update to the Ptenum family (affecting especially the ptemalfind plugin), which makes the plugins reliable in identifying modified pages despite memory combining, so make sure to grab the newest version from the Github repository.

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Process Hollowing is a technique used by various malware families (such as FormBook, TrickBot and Agent Tesla) to hide their malicious code within a benign appearing process. The typical workflow for setting up such a hollowed process is as follows:

1. Create a new process (victim) using a benign executable, in suspended state.
2. Unmap the executable from that process.
3. Allocate memory for the malicious executable at the address of the previously mapped victim executable.
4. Write the malicious executable to the new memory area and potentially apply relocations.
5. Adjust the entry point.
6. Resume process.

We will refer to this as the “normal” Process Hollowing workflow. There are also variants of this technique, one being to not unmap the original executable and to allocate the new memory somewhere else. We will call this one no-unmap. But wait, why does malware not simply overwrite the existing executable but creates a new memory area which stands out due to its characteristics? In this blog post we will have a closer look at this overwrite approach but also on the no-unmap method, their effects on analysis/detection tools and on some tricks to make the detection harder. We are also releasing Proof of Concept implementations of all mentioned tools/plugins (the links are at the end of this post).

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I’m happy to announce the release of several plugins for Volatility 3 that allow you to dig deeper into the memory analysis. One of those plugins is PteMalfind, which is essentially an improved version of malfind. Another one is PteResolve which, similarly to the WinDBG command !pte, allows you to inspect Page Table Entry (PTE) information for e.g., a given virtual address. In this blog post we will have a closer look at these and more plugins, and the PteEnumerator base class and what you can do with it. The memory dump used for this blog post is available here. Some of the injection tools used in this blog post can be gathered from here.

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After our last blogpost regarding Emotet and several other Emotet and Ransomware samples that we encountered, we recently stumbled across a variant belonging to the Gozi, ISFB, Dreambot respectively Ursnif family. In this blogpost, we want to share our insights from the analysis of this malware, whose malware family is mainly known for being a banking trojan that typically tries to infect browser sessions and sniff/redirect data. In particular, we are going to provide details about the first stage Word Document, the embedded JavaScript/XSL document, an in-depth runtime analysis of the downloaded executable, and some details regarding detection.

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After quite some time and work, I’m happy to announce the new release of the Linux Heap Analysis Plugins, which are now part of the Rekall project, but not yet part of an official Rekall release, so you have to grab them manually.
This release fixes several bugs and adds the following features:

• Support for Glibc version 2.26 (tcache chunks) and 2.27
• Heapsearch now includes Rekall’s yara scan functionality
• x86 Glibc versions with a modified MALLOC_ALIGNMENT value of 16 (as done in arch’s glibc package 2.26) are now supported
• Improved retrieval of main_arena and new automated retrieval of malloc_par struct; so for the majority of cases, the corresponding cmd line options are not necessary anymore and hence no debug information have to be retrieved.
• main_arena and malloc_par struct retrieval now also applies for statically linked binaries; there might however be cases, where it is necessary to specify the malloc_par struct offset and the used glibc version number

While Glibc version 2.27 does not really change much for the heap from a forensics point of view, version 2.26 introduced a new feature called tcache (per thread cache). Those caches are essentially just a new type of bin, holding freed chunks, but seem to improve the performance.
Sadly, only two days after its first commit, there was already a blog post explaining the functionality (not so sad 😉 ) and also some discovered vulnerabilities (here we go with the sad part).
Besides introducing a new landscape for attackers, this feature added two new heap management structs and one additional chunk per thread-heap (each thread has its own heap, up until an upper limit). This chunk is located at the beginning of each heap and hence, part of a raw heap dump (so be aware of that, if you are doing a raw analysis without the plugins).
The chunk holds the content of the tcache_perthread_struct, which has to members:

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As mentioned in my last blogpost, I had the pleasure to participate in this years DFRWS USA and present our paper. The paper and presentation can be freely viewed and downloaded here or here. Note that there is also an extended version of the paper, which can be downloaded here.

The keepassx, zsh and heap analysis plugins are now also part of the Rekall release candidate 1.7.0RC1, so it’s easier to get started.

The conference had some great talks and workshops, which I’m going to briefly sum up.

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I’m happy to announce the release of several Glibc heap analysis plugins (for Linux), resp. plugins to gather information from keepassx and zsh, which are now included in the Rekall Memory Forensic Framework. This blogpost will demonstrate these plugins and explain how they can be used. More detailed information, including real world scenarios, will be released after the talk at this years DFRWS USA.

Before being able to reliably analyze the heap of a process, a profile, for the Glibc version being used, must be provided. However, this step should for most cases be fairly simple and only consist of gathering the offset for the mp_ and main_arena variables:

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While doing heap research on Linux processes (results are going to be published soon), I came across the bot from the Mirai Botnet. As already mentioned in the blog post by Brian, the Mirai bot uses obfuscated configuration data which contains e.g. the CnC server. When now confronted only with a bot (e.g. in the context of a running task or the ELF binary), but without the according source code, the decryption of this configuration data for e.g. incident analysis purposes might not be easily possible (with the python script from the blog post), if the key has been changed.
But in this case that is not a problem at all, because

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As we are giving another round of our Incident Analysis workshop at Troopers16, we wanted to give a little sample taste what you can expect.

Table of Contents
Extracting Mail Attachments
Word Document Analysis
Static JavaScript Analysis
Dynamic JavaScript Analysis

Before we dive into the analysis, I wanted to mention that if you are going to analyze anything unknown/potentially malicious, do it in a safe environment (VM with no internet connection, in the best case on a separate physical analysis device, or at least strip all unnecessary functionality from that VM (CVE-2015-3456 is an example to answer the “why”)). Even things like looking at content with a text editor or extracting zip files should be done in the safe environment, as those tools could contain vulnerabilities.

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In this blogpost we will briefly explain a well known Syscall hooking technique (a more detailed explanation can be gathered from e.g.  http://resources.infosecinstitute.com/hooking-system-service-dispatch-table-ssdt/) used by multiple malware samples (like the laqma trojan) and right after discuss how some memory analysis tools have trouble in the analysis and/or reporting of these.

Before we go further, I just shortly wanted to say, that this post is not intended to be a bashing of any tool. We have the greatest respect for all the effort and work which has been and most probably will be done in the future.

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