memory-forensics

内存取证

全面介绍在事件响应和恶意软件分析中获取、分析和提取内存转储中的工件的技术。

在以下情况下使用此技能

• 处理内存取证任务或工作流
• 需要内存取证方面的指导、最佳实践或检查清单

在以下情况下请勿使用此技能

• 任务与内存取证无关
• 需要使用超出此范围的其他领域知识或工具

说明

• 明确目标、约束条件和所需输入。
• 运用相关最佳实践并验证结果。
• 提供可执行的步骤和验证方法。

内存获取

采集前，确认已获得针对特定主机/VM 以及敏感内存采集的授权。转储可能包含密码、私钥和个人记录：应加密存储并限制访问，为原始文件计算哈希，记录工具、版本、时间和保管链，并在离线环境中分析副本。未经明确授权，不得将转储或凭据输出上传到外部服务。凭据提取插件属于单独的敏感步骤，并非常规初步检查的一部分。

采集可能导致实时系统暂停、崩溃或受到影响。使用可信且兼容目标操作系统的工具，确认输出容量并记录完整性；/dev/mem 通常受到限制，而 /proc/kcore 是稀疏虚拟视图，不能替代经过验证的物理内存采集。旧版 macOS 工具可能不支持目标硬件/操作系统。这里没有任何采集命令能保证普遍安全。

实时采集工具

Windows

# WinPmem (Recommended)
winpmem_mini_x64.exe memory.raw

# DumpIt
DumpIt.exe

# Belkasoft RAM Capturer
# GUI-based, outputs raw format

# Magnet RAM Capture
# GUI-based, outputs raw format

Linux

# LiME (Linux Memory Extractor)
sudo insmod lime.ko "path=/tmp/memory.lime format=lime"

# /dev/mem (limited, requires permissions)
sudo dd if=/dev/mem of=memory.raw bs=1M

# /proc/kcore (ELF format)
sudo cp /proc/kcore memory.elf

macOS

# osxpmem
sudo ./osxpmem -o memory.raw

# MacQuisition (commercial)

虚拟机内存

# VMware: .vmem file is raw memory
cp vm.vmem memory.raw

# VirtualBox: Use debug console
vboxmanage debugvm "VMName" dumpvmcore --filename memory.elf

# QEMU
virsh dump <domain> memory.raw --memory-only

# Hyper-V
# Checkpoint contains memory state

Volatility 3 框架

使用已安装版本的帮助信息确认可用插件及其选项。以下部分名称可能属于旧版或特定版本；不要假定 Volatility 2 的所有插件或转储标志在 Volatility 3 中都存在。结构示例仅供概念参考，具体取决于操作系统版本。YARA 匹配结果、进程列表差异和可执行内存都只是需要进一步关联分析的线索，不能单独作为恶意软件存在的证据。

安装和设置

# Install Volatility 3
pip install volatility3

# Install symbol tables (Windows)
# Download from https://downloads.volatilityfoundation.org/volatility3/symbols/

# Basic usage
vol -f memory.raw <plugin>

# With symbol path
vol -f memory.raw -s /path/to/symbols windows.pslist

基本插件

进程分析

# List processes
vol -f memory.raw windows.pslist

# Process tree (parent-child relationships)
vol -f memory.raw windows.pstree

# Hidden process detection
vol -f memory.raw windows.psscan

# Process memory dumps
vol -f memory.raw windows.memmap --pid <PID> --dump

# Process environment variables
vol -f memory.raw windows.envars --pid <PID>

# Command line arguments
vol -f memory.raw windows.cmdline

网络分析

# Network connections
vol -f memory.raw windows.netscan

# Network connection state
vol -f memory.raw windows.netstat

DLL 和模块分析

# Loaded DLLs per process
vol -f memory.raw windows.dlllist --pid <PID>

# Find hidden/injected DLLs
vol -f memory.raw windows.ldrmodules

# Kernel modules
vol -f memory.raw windows.modules

# Module dumps
vol -f memory.raw windows.moddump --pid <PID>

内存注入检测

# Detect code injection
vol -f memory.raw windows.malfind

# VAD (Virtual Address Descriptor) analysis
vol -f memory.raw windows.vadinfo --pid <PID>

# Dump suspicious memory regions
vol -f memory.raw windows.vadyarascan --yara-rules rules.yar

注册表分析

# List registry hives
vol -f memory.raw windows.registry.hivelist

# Print registry key
vol -f memory.raw windows.registry.printkey --key "Software\Microsoft\Windows\CurrentVersion\Run"

# Dump registry hive
vol -f memory.raw windows.registry.hivescan --dump

文件系统工件

# Scan for file objects
vol -f memory.raw windows.filescan

# Dump files from memory
vol -f memory.raw windows.dumpfiles --pid <PID>

# MFT analysis
vol -f memory.raw windows.mftscan

Linux 分析

# Process listing
vol -f memory.raw linux.pslist

# Process tree
vol -f memory.raw linux.pstree

# Bash history
vol -f memory.raw linux.bash

# Network connections
vol -f memory.raw linux.sockstat

# Loaded kernel modules
vol -f memory.raw linux.lsmod

# Mount points
vol -f memory.raw linux.mount

# Environment variables
vol -f memory.raw linux.envars

macOS 分析

# Process listing
vol -f memory.raw mac.pslist

# Process tree
vol -f memory.raw mac.pstree

# Network connections
vol -f memory.raw mac.netstat

# Kernel extensions
vol -f memory.raw mac.lsmod

分析工作流

恶意软件分析工作流

# 1. Initial process survey
vol -f memory.raw windows.pstree > processes.txt
vol -f memory.raw windows.pslist > pslist.txt

# 2. Network connections
vol -f memory.raw windows.netscan > network.txt

# 3. Detect injection
vol -f memory.raw windows.malfind > malfind.txt

# 4. Analyze suspicious processes
vol -f memory.raw windows.dlllist --pid <PID>
vol -f memory.raw windows.handles --pid <PID>

# 5. Dump suspicious executables
vol -f memory.raw windows.pslist --pid <PID> --dump

# 6. Extract strings from dumps
strings -a pid.<PID>.exe > strings.txt

# 7. YARA scanning
vol -f memory.raw windows.yarascan --yara-rules malware.yar

事件响应工作流

# 1. Timeline of events
vol -f memory.raw windows.timeliner > timeline.csv

# 2. User activity
vol -f memory.raw windows.cmdline
vol -f memory.raw windows.consoles

# 3. Persistence mechanisms
vol -f memory.raw windows.registry.printkey \
    --key "Software\Microsoft\Windows\CurrentVersion\Run"

# 4. Services
vol -f memory.raw windows.svcscan

# 5. Scheduled tasks
vol -f memory.raw windows.scheduled_tasks

# 6. Recent files
vol -f memory.raw windows.filescan | grep -i "recent"

数据结构

Windows 进程结构

// EPROCESS (Executive Process)
typedef struct _EPROCESS {
    KPROCESS Pcb;                    // Kernel process block
    EX_PUSH_LOCK ProcessLock;
    LARGE_INTEGER CreateTime;
    LARGE_INTEGER ExitTime;
    // ...
    LIST_ENTRY ActiveProcessLinks;   // Doubly-linked list
    ULONG_PTR UniqueProcessId;       // PID
    // ...
    PEB* Peb;                        // Process Environment Block
    // ...
} EPROCESS;

// PEB (Process Environment Block)
typedef struct _PEB {
    BOOLEAN InheritedAddressSpace;
    BOOLEAN ReadImageFileExecOptions;
    BOOLEAN BeingDebugged;           // Anti-debug check
    // ...
    PVOID ImageBaseAddress;          // Base address of executable
    PPEB_LDR_DATA Ldr;              // Loader data (DLL list)
    PRTL_USER_PROCESS_PARAMETERS ProcessParameters;
    // ...
} PEB;

VAD（虚拟地址描述符）

typedef struct _MMVAD {
    MMVAD_SHORT Core;
    union {
        ULONG LongFlags;
        MMVAD_FLAGS VadFlags;
    } u;
    // ...
    PVOID FirstPrototypePte;
    PVOID LastContiguousPte;
    // ...
    PFILE_OBJECT FileObject;
} MMVAD;

// Memory protection flags
#define PAGE_EXECUTE           0x10
#define PAGE_EXECUTE_READ      0x20
#define PAGE_EXECUTE_READWRITE 0x40
#define PAGE_EXECUTE_WRITECOPY 0x80

检测模式

进程注入指标

# Malfind indicators
# - PAGE_EXECUTE_READWRITE protection (suspicious)
# - MZ header in non-image VAD region
# - Shellcode patterns at allocation start

# Common injection techniques
# 1. Classic DLL Injection
#    - VirtualAllocEx + WriteProcessMemory + CreateRemoteThread

# 2. Process Hollowing
#    - CreateProcess (SUSPENDED) + NtUnmapViewOfSection + WriteProcessMemory

# 3. APC Injection
#    - QueueUserAPC targeting alertable threads

# 4. Thread Execution Hijacking
#    - SuspendThread + SetThreadContext + ResumeThread

Rootkit 检测

# Compare process lists
vol -f memory.raw windows.pslist > pslist.txt
vol -f memory.raw windows.psscan > psscan.txt
diff pslist.txt psscan.txt  # Hidden processes

# Check for DKOM (Direct Kernel Object Manipulation)
vol -f memory.raw windows.callbacks

# Detect hooked functions
vol -f memory.raw windows.ssdt  # System Service Descriptor Table

# Driver analysis
vol -f memory.raw windows.driverscan
vol -f memory.raw windows.driverirp

凭据提取

# Dump hashes (requires hivelist first)
vol -f memory.raw windows.hashdump

# LSA secrets
vol -f memory.raw windows.lsadump

# Cached domain credentials
vol -f memory.raw windows.cachedump

# Mimikatz-style extraction
# Requires specific plugins/tools

YARA 集成

编写内存 YARA 规则

rule Suspicious_Injection
{
    meta:
        description = "Detects common injection shellcode"

    strings:
        // Common shellcode patterns
        $mz = { 4D 5A }
        $shellcode1 = { 55 8B EC 83 EC }  // Function prologue
        $api_hash = { 68 ?? ?? ?? ?? 68 ?? ?? ?? ?? E8 }  // Push hash, call

    condition:
        $mz at 0 or any of ($shellcode*)
}

rule Cobalt_Strike_Beacon
{
    meta:
        description = "Detects Cobalt Strike beacon in memory"

    strings:
        $config = { 00 01 00 01 00 02 }
        $sleep = "sleeptime"
        $beacon = "%s (admin)" wide

    condition:
        2 of them
}

扫描内存

# Scan all process memory
vol -f memory.raw windows.yarascan --yara-rules rules.yar

# Scan specific process
vol -f memory.raw windows.yarascan --yara-rules rules.yar --pid 1234

# Scan kernel memory
vol -f memory.raw windows.yarascan --yara-rules rules.yar --kernel

字符串分析

提取字符串

# Basic string extraction
strings -a memory.raw > all_strings.txt

# Unicode strings
strings -el memory.raw >> all_strings.txt

# Targeted extraction from process dump
vol -f memory.raw windows.memmap --pid 1234 --dump
strings -a pid.1234.dmp > process_strings.txt

# Pattern matching
grep -E "(https?://|[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3})" all_strings.txt

使用 FLOSS 分析混淆字符串

# FLOSS extracts obfuscated strings
floss malware.exe > floss_output.txt

# From memory dump
floss pid.1234.dmp

最佳实践

采集最佳实践

1. 尽量减少影响：使用轻量级采集工具
2. 记录所有信息：记录采集时间、工具和采集文件的哈希
3. 验证完整性：采集后立即计算内存转储的哈希
4. 保管链：遵循规范的取证处理流程

分析最佳实践

1. 先整体后局部：深入分析前先掌握整体情况
2. 交叉验证：使用多个插件分析同一数据
3. 关联时间线：将内存发现与磁盘/网络信息进行关联
4. 记录发现：详细记录笔记并保存截图
5. 验证结果：通过多种方法验证发现

常见陷阱

• 数据过时：内存具有易失性，应及时分析
• 转储不完整：确认转储大小与预期 RAM 容量相符
• 符号问题：确保符号文件与操作系统版本相符
• 数据混杂：采集期间内存可能发生变化
• 加密：部分数据在内存中可能经过加密

限制

• 仅当任务明确符合上述范围时，才使用此技能。
• 不要将输出视为特定环境验证、测试或专家评审的替代品。
• 如果缺少必需的输入、权限、安全边界或成功标准，请停止并请求澄清。