Scanning memory with Yara

Memory analysis has been successfully utilized to detect malware in many high profile cases. The use of signature scanning to detect malicious tools is becoming an effective triaging and first response technique. In particular, the Yara library and scanner has emerged as the defacto standard in malware signature scanning for files, and there are many open source repositories of yara rules. Previous attempts to incorporate yara scanning in memory analysis yielded mixed results. This paper examines the differences between applying Yara signatures on files and in memory and how yara signatures can be developed to effectively search for malware in memory. For the first time we document a technique to identify the process owner of a physical page using the Windows PFN database. We use this to develop a context aware Yara scanning engine which can scan all processes simultaneously using a single pass over the physical image.     

Surveying the user space through user allocations

Previous research into memory forensics has focused on understanding the structure and contents of the kernel space portions of physical memory, and mostly ignored the contents of the user space. This paper describes the results of a survey of user space virtual address allocations in the Windows XP and Windows 7 operating systems, comprehensively identifying the kernel and user space metadata required to identify such allocations. New techniques for determining the role and content of those allocations are identified, significantly increasing the proportion of allocations for which the role and function is understood. The validity of this approach is evaluated and a detailed analysis of the data structures involved provided. An implementation of this approach is presented which is capable of identifying all user space allocations, and for those allocations identifying for a high percentage, the role of those allocations, even for complex applications.     

针对进程用户空间的电子数据取证方法研究

进程用户空间中的信息往往与特定用户的特定操作行为直接关联,对于证据链的建立意义重大.从数目繁多的用户空间数据结构中筛选出最重要的三种：进程环境块、线程环境块与虚拟地址描述符,说明其定位方法,并重点讨论其结构格式的电子数据取证特性,为内存空间电子数据取证提供了新的思路与方法.实例分析部分,则以目前广泛使用的Windows 7操作系统为应用背景,说明了所述方法的具体应用.     

Scalable code clone search for malware analysis

Reverse engineering is the primary step to analyze a piece of malware. After having disassembled a malware binary, a reverse engineer needs to spend extensive effort analyzing the resulting assembly code, and then documenting it through comments in the assembly code for future references. In this paper, we have developed an assembly code clone search system called ScalClone based on our previous work on assembly code clone detection systems. The objective of the system is to identify the code clones of a target malware from a collection of previously analyzed malware binaries. Our new contributions are summarized as follows: First, we introduce two assembly code clone search methods for malware analysis with a high recall rate. Second, our methods allow malware analysts to discover both exact and inexact clones at different token normalization levels. Third, we present a scalable system with a database model to support large-scale assembly code search. Finally, experimental results on real-life malware binaries suggest that our proposed methods can effectively identify assembly code clones with the consideration of different scenarios of code mutations.     

Forensic memory analysis: From stack and code to execution history

Forensics memory analysis has recently gained great attention in cyber forensics community. However, most of the proposals have focused on the extraction of important kernel data structures such as executive objects from the memory. In this paper, we propose a formal approach to analyze the stack memory of process threads to discover a partial execution history of the process. Our approach uses a process logic to model the extracted properties from the stack and then verify these properties against models generated from the program assembly code. The main focus of the paper is on Windows thread stack analysis though the same idea is applicable to other operating systems.     

User data persistence in physical memory

In this paper we present the results of experiments we conducted on Suse Linux and Windows XP systems to determine the age of user process data in physical memory. To be able to measure the age of pages we used an artificial load program which time-stamps data segment and block device cache pages. Our goal was to compare the behaviour of both systems and to determine whether the rate of decay for user data depends on the demand for physical memory. Our findings show that Windows and Linux systems preserve almost the same number of pages with user data, and the age distribution of these pages does not change significantly with the level of demand.     

A Forensic Exploration of the Microsoft Windows 10 Timeline

The Microsoft Windows operating system continues to dominate the desktop computing market. With such high levels of usage comes an inferred likelihood of digital forensic practitioners encountering this platform during their investigations. As part of any forensic examination of a digital device, operating system artifacts, which support the identification and understanding of how a user has behaved on their system provide a potential source of evidence. Now, following Microsoft's April 2018 build 1803 release with its incorporated “Timeline” feature, the potential for identifying and tracking user activity has increased. This work provides a timely examination of the Windows 10 Timeline feature demonstrating the ability to recover activity‐based content from within its stored database log files. Examination results and underpinning experimental methodologies are offered, demonstrating the ability to recover activity tile and process information in conjunction with the Windows Timeline. Further, an SQL query has been provided to support the interpretation of data stored within the ActivitiesCache.db .     

Forensic carving of network packets and associated data structures

Using validated carving techniques, we show that popular operating systems (e.g. Windows, Linux, and OSX) frequently have residual IP packets, Ethernet frames, and associated data structures present in system memory from long-terminated network traffic. Such information is useful for many forensic purposes including establishment of prior connection activity and services used; identification of other systems present on the system’s LAN or WLAN; geolocation of the host computer system; and cross-drive analysis. We show that network structures can also be recovered from memory that is persisted onto a mass storage medium during the course of system swapping or hibernation. We present our network carving techniques, algorithms and tools, and validate these against both purpose-built memory images and a readily available forensic corpora. These techniques are valuable to both forensics tasks, particularly in analyzing mobile devices, and to cyber-security objectives such as malware analysis.     

Using shellbag information to reconstruct user activities

Built into Microsoft Windows is the ability for the operating system to track user window viewing preferences specific to Windows Explorer. This information, which is called “ShellBag” information, is stored in several locations within the Windows Registry in the Windows Operating System. This paper introduces a novel method to examine ShellBag information within Registry snapshots to reconstruct user activities. It compares different states of ShellBag information within consecutive Registry snapshots in order to detect ShellBag-related user actions. Nine detection rules are proposed on the basis of analyzing the causality between user actions and updated ShellBag information. This approach can be used to prove that certain interactions between the user and system must have, or must not have happened during a certain time period.     

USB Storage Device Forensics for Windows 10

Significantly increased use of USB devices due to their user‐friendliness and large storage capacities poses various threats for many users/companies in terms of data theft that becomes easier due to their efficient mobility. Investigations for such data theft activities would require gathering critical digital information capable of recovering digital forensics artifacts like date, time, and device information. This research gathers three sets of registry and logs data: first, before insertion; second, during insertion; and the third, after removal of a USB device. These sets are analyzed to gather evidentiary information from Registry and Windows Event log that helps in tracking a USB device. This research furthers the prior research on earlier versions of Microsoft Windows and compares it with latest Windows 10 system. Comparison of Windows 8 and Windows 10 does not show much difference except for new subkey under USB Key in registry. However, comparison of Windows 7 with latest version indicates significant variances.     

Exploiting the post-attendee URL feature in Zoom webinar to distribute malware

The post-attendee Uniform Resource Locator (URL) feature within the video conferencing application known as Zoom is often overlooked by digital forensic experts as a potential risk for malware transmission. However, with the ability to redirect webinar participants to any URL set by the host for the webinar, the post-attendee URL can be abused by bad actors to expose webinar participants to malicious websites or, in the worst-case scenario, force participants to download a file through the use of a direct download link URL. This study aims to showcase how this exploit can be replicated by creating an experimental environment involving four Windows 10 desktops running Zoom version 5.7.5 and creating a webinar with four user accounts acting as webinar participants and setting the post-attendee URL value to the URL of a website that contained a keylogger. In another trial, the same experimental environment was utilized, with the only difference being the post-attendee URL that was set to redirect webinar participants to a download link for a .jpg file. In both instances, every user account that joined the webinar via clicking on the invitation link that was emailed to each user account after registering for the webinar was redirected to the post-attendee URL regardless of their user account role. These results not only prove that the post-attendee URL can be exploited, but also provide insight as to how this type of attack can be prevented.     

Anti-forensic resilient memory acquisition

Memory analysis has gained popularity in recent years proving to be an effective technique for uncovering malware in compromised computer systems. The process of memory acquisition presents unique evidentiary challenges since many acquisition techniques require code to be run on a potential compromised system, presenting an avenue for anti-forensic subversion. In this paper, we examine a number of simple anti-forensic techniques and test a representative sample of current commercial and free memory acquisition tools. We find that current tools are not resilient to very simple anti-forensic measures. We present a novel memory acquisition technique, based on direct page table manipulation and PCI hardware introspection, without relying on operating system facilities - making it more difficult to subvert. We then evaluate this technique's further vulnerability to subversion by considering more advanced anti-forensic attacks.     

Obtaining forensic value from the cbWndExtra structures as used by Windows Common Controls,specifically for the Editbox control

The Windows Common Controls is a library which facilitates the construction of GUI controls commonly used by Windows applications. Each control is an extension of the basic ‘window’ class. The difference in the extension results in one control over another; for example, an Edit control as opposed to a Button control. The basic window class is documented by Microsoft and the generic information about a Window can be extracted, but this is of very limited use. There is no documentation and very little research into how these extensions are laid out in memory. This paper demonstrates how the extension bytes for the Edit control can be parsed leading to identification of previously unobtainable data which reveal information about the state of the control at runtime. Most notably, the undo buffer, that is, text that was previously present in the control can be recovered – an aspect which traditional disk forensics would simply not provide. The paper explains why previous attempts to achieve similar goals have failed, and how the technique could be applied to any control from the Windows Common Controls library.     

Forensic analysis of Telegram Messenger for Windows Phone

This article presents a forensic analysis methodology for obtaining the digital evidence generated by one of today's many instant messaging applications, namely “Telegram Messenger” for “Windows Phone”, paying particular attention to the digital forensic artifacts produced. The paper provides an overview of this forensic analysis, while focusing particularly on how the information is structured and the user, chat and conversation data generated by the application are organised, with the goal of extracting related data from the information. The application has several other features (e.g. games, bots, stickers) besides those of an instant messaging application (e.g. messages, images, videos, files). It is therefore necessary to decode and interpret the information, which may relate to criminal offences, and establish the relation of different types of user, chat and conversation.     

Windows Surface RT tablet forensics

Small scale digital device forensics is particularly critical as a result of the mobility of these devices, leading to closer proximity to crimes as they occur when compared to computers. The Windows Surface tablet is one such device, combining tablet mobility with familiar Microsoft Windows productivity tools. This research considers the acquisition and forensic analysis of the Windows Surface RT tablet. We discuss the artifacts of both the Windows RT operating system and third-party applications. The contribution of this research is to provide a road map for the digital forensic examination of Windows Surface RT tablets.     

Extracting Windows command line details from physical memory

Current memory forensic tools concentrate mainly on system-related information like processes and sockets. There is a need for more memory forensic techniques to extract user-entered data retained in various Microsoft Windows applications such as the Windows command prompt. The command history is a prime source of evidence in many intrusions and other computer crimes, revealing important details about an offender’s activities on the subject system. This paper dissects the data structures of the command prompt history and gives forensic practitioners a tool for reconstructing the Windows command history from a Windows XP memory capture. At the same time, this paper demonstrates a methodology that can be generalized to extract user-entered data on other versions of Windows.     

A comparison of forensic evidence recovery techniques for a windows mobile smart phone

Acquisition, decoding and presentation of information from mobile devices is complex and challenging. Device memory is usually integrated into the device, making isolation prior to recovery difficult. In addition, manufacturers have adopted a variety of file systems and formats complicating decoding and presentation.A variety of tools and methods have been developed (both commercially and in the open source community) to assist mobile forensics investigators. However, it is unclear to what extent these tools can present a complete view of the information held on a mobile device, or the extent the results produced by different tools are consistent.This paper investigates what information held on a Windows Mobile smart phone can be recovered using several different approaches to acquisition and decoding. The paper demonstrates that no one technique recovers all information of potential forensic interest from a Windows Mobile device; and that in some cases the information recovered is conflicting.     

逆向分析在电子数据取证中的应用——以“QQ密码大划拉”为例

逆向分析是恶意程序取证的常用方法之一,在揭示恶意程序意图及行为方面发挥着其他方法无法比拟的作用。在对逆向分析基本概念、方法、工具进行介绍的基础上,结合中国大陆地区一起利用恶意程序窃取QQ账号与密码的真实案例,从查壳、脱壳、断点设置、程序跟踪、关键信息获取等方面详细描述了针对恶意程序进行逆向分析的全过程。     

In‐Depth Analysis of Computer Memory Acquisition Software for Forensic Purposes

The comparison studies on random access memory (RAM) acquisition tools are either limited in metrics or the selected tools were designed to be executed in older operating systems. Therefore, this study evaluates widely used seven shareware or freeware/open source RAM acquisition forensic tools that are compatible to work with the latest 64‐bit Windows operating systems. These tools' user interface capabilities, platform limitations, reporting capabilities, total execution time, shared and proprietary DLLs, modified registry keys, and invoked files during processing were compared. We observed that Windows Memory Reader and Belkasoft's Live Ram Capturer leaves the least fingerprints in memory when loaded. On the other hand, ProDiscover and FTK Imager perform poor in memory usage, processing time, DLL usage, and not‐wanted artifacts introduced to the system. While Belkasoft's Live Ram Capturer is the fastest to obtain an image of the memory, Pro Discover takes the longest time to do the same job.     

Bin-Carver: Automatic recovery of binary executable files

File carving is the process of reassembling files from disk fragments based on the file content in the absence of file system metadata. By leveraging both file header and footer pairs, traditional file carving mainly focuses on document and image files such as PDF and JPEG. With the vast amount of malware code appearing in the wild daily, recovery of binary executable files becomes an important problem, especially for the case in which malware deletes itself after compromising a computer. However, unlike image files that usually have both a header and footer pair, executable files only have header information, which makes the carving much harder. In this paper, we present Bin-Carver, a first-of-its-kind system to automatically recover executable files with deleted or corrupted metadata. The key idea is to explore the road map information defined in executable file headers and the explicit control flow paths present in the binary code. Our experiment with thousands of binary code files has shown our Bin-Carver to be incredibly accurate, with an identification rate of 96.3% and recovery rate of 93.1% on average when handling file systems ranging from pristine to chaotic and highly fragmented.