detecting-evasion-techniques-in-endpoint-logs

检测终端日志中的规避技术

何时使用

在以下情况下使用本技能：

• 在终端遥测数据中搜寻攻击者的防御规避技术（MITRE ATT&CK TA0005）
• 为常见规避方法（进程注入、时间戳篡改、日志清除）构建检测规则
• 调查攻击者禁用或绕过安全工具的 incident
• 分析终端日志，寻找离地攻击二进制（LOLBin）滥用的指标

不要使用本技能来处理网络层规避（请使用网络流量分析）或恶意软件逆向工程。

前置条件

• 已安装并配置 Sysmon，且具备全面的日志记录规则（SwiftOnSecurity 或 Olaf Hartong 配置）
• 已启用高级审核策略的 Windows 安全事件日志
• EDR 遥测（CrowdStrike、SentinelOne、Microsoft Defender for Endpoint）
• 用于日志关联的 SIEM 平台（Splunk、Elastic、Sentinel）
• 用于技术参考的 MITRE ATT&CK Enterprise 矩阵

工作流

第 1 步：检测日志篡改（T1070）

Windows 事件日志清除（T1070.001）：

# Sysmon Event ID 1 (Process Create) for wevtutil
EventID: 1
CommandLine contains: "wevtutil cl" OR "wevtutil clear-log"

# Security Event ID 1102 - Audit log was cleared
EventID: 1102
Source: Microsoft-Windows-Eventlog

# System Event ID 104 - Event log was cleared
EventID: 104

# PowerShell log clearing
EventID: 1 (Sysmon)
CommandLine contains: "Clear-EventLog" OR "Remove-EventLog"

# Splunk query:
index=windows (EventCode=1102 OR EventCode=104)
  OR (EventCode=1 CommandLine="*wevtutil*cl*")
  OR (EventCode=1 CommandLine="*Clear-EventLog*")
| table _time host user CommandLine EventCode

时间戳篡改（T1070.006）：

# Sysmon Event ID 2 - File creation time changed
EventID: 2
# Look for creation times set far in the past on recently-written files
# Correlate with Event ID 11 (FileCreate) - if FileCreate is recent but
# creation time in Event ID 2 is old, timestomping is likely

# MDE Advanced Hunting (KQL):
DeviceFileEvents
| where ActionType == "FileTimestampModified"
| where Timestamp > ago(7d)
| extend TimeDiff = datetime_diff('day', Timestamp, ReportedFileCreationTime)
| where TimeDiff > 30
| project Timestamp, DeviceName, FileName, FolderPath,
    ReportedFileCreationTime, InitiatingProcessFileName

第 2 步：检测进程注入（T1055）

# Sysmon Event ID 8 - CreateRemoteThread
EventID: 8
# Alert when source process is unusual (not system processes)
# Filter out known legitimate: antivirus, debugging tools
SourceImage NOT IN ("C:\Windows\System32\csrss.exe",
                     "C:\Windows\System32\lsass.exe")

# Sysmon Event ID 10 - ProcessAccess with suspicious access masks
EventID: 10
GrantedAccess contains: "0x1F0FFF" OR "0x1FFFFF" OR "0x001F0FFF"
# PROCESS_ALL_ACCESS = 0x1F0FFF (common in injection)
# Filter legitimate: AV accessing all processes

# Sysmon Event ID 25 - Process Tampering
EventID: 25
Type: "Image is replaced"  # Process hollowing indicator

# Splunk detection:
index=sysmon EventCode=8
| where NOT match(SourceImage, "(?i)(csrss|svchost|MsMpEng|defender)")
| stats count by SourceImage TargetImage host
| where count < 5
| sort - count

第 3 步：检测安全工具被禁用（T1562）

# Service stopped events for security services
EventID: 7045 (new service) OR 7036 (service state change)
ServiceName IN ("WinDefend", "Sense", "CrowdStrike Falcon Sensor",
                 "SentinelAgent", "csagent", "MBAMService")

# Sysmon Event ID 1 - Processes that disable Defender
CommandLine contains: "Set-MpPreference -DisableRealtimeMonitoring"
  OR "sc stop WinDefend"
  OR "sc config WinDefend start= disabled"
  OR "net stop" AND ("windefend" OR "sense" OR "csagent")

# Registry modification to disable security features
# Sysmon Event ID 13 - Registry value set
TargetObject contains: "DisableAntiSpyware"
  OR "DisableRealtimeMonitoring"
  OR "DisableBehaviorMonitoring"
Details: "DWORD (0x00000001)"

# MDE KQL:
DeviceRegistryEvents
| where RegistryValueName in ("DisableAntiSpyware", "DisableRealtimeMonitoring")
| where RegistryValueData == "1"
| project Timestamp, DeviceName, RegistryKey, InitiatingProcessFileName

第 4 步：检测伪装（T1036）

# Sysmon Event ID 1 - Process with legitimate name from unusual path
EventID: 1
Image contains: "svchost.exe" AND Image NOT starts with: "C:\Windows\System32\"
Image contains: "csrss.exe" AND Image NOT starts with: "C:\Windows\System32\"
Image contains: "lsass.exe" AND Image NOT starts with: "C:\Windows\System32\"

# Process name mismatch (original filename vs. current name)
# Sysmon captures OriginalFileName from PE header
EventID: 1
OriginalFileName != (parsed filename from Image path)

# Double extension files
EventID: 11 (FileCreate)
TargetFilename matches: "*\.pdf\.exe" OR "*\.doc\.exe" OR "*\.jpg\.exe"

# Splunk:
index=sysmon EventCode=1
| eval process_name=mvindex(split(Image,"\\"),-1)
| where (process_name="svchost.exe" AND NOT match(Image,"(?i)C:\\\\Windows\\\\System32"))
  OR (process_name="csrss.exe" AND NOT match(Image,"(?i)C:\\\\Windows\\\\System32"))
| table _time host Image ParentImage CommandLine User

第 5 步：检测 LOLBin 滥用（T1218、T1127）

# Common LOLBin abuse patterns:

# mshta.exe executing remote content
EventID: 1
Image ends with: "mshta.exe"
CommandLine contains: "http" OR "javascript:" OR "vbscript:"

# certutil.exe downloading files
EventID: 1
Image ends with: "certutil.exe"
CommandLine contains: "-urlcache" OR "-decode" OR "-encode"

# regsvr32.exe executing scriptlets
EventID: 1
Image ends with: "regsvr32.exe"
CommandLine contains: "/s /n /u /i:" OR "scrobj.dll"

# rundll32.exe with unusual DLLs
EventID: 1
Image ends with: "rundll32.exe"
CommandLine contains: "javascript:" OR ".js" OR "http:"

# MSBuild executing inline tasks
EventID: 1
Image contains: "MSBuild.exe"
CommandLine NOT contains: ".sln" AND NOT contains: ".csproj"

第 6 步：构建检测规则关联

# Combine multiple weak signals into high-confidence detection:

# Rule: Potential post-exploitation evasion chain
# Trigger when 3+ evasion techniques observed on same host within 1 hour

# Splunk correlation search:
index=sysmon host=*
| eval technique=case(
    EventCode=2, "timestomping",
    EventCode=8 AND NOT match(SourceImage,"csrss|svchost"), "process_injection",
    EventCode=1 AND match(CommandLine,"(?i)wevtutil.*cl"), "log_clearing",
    EventCode=13 AND match(TargetObject,"DisableRealtimeMonitoring"), "security_disable",
    EventCode=1 AND match(CommandLine,"(?i)(mshta|certutil.*urlcache|regsvr32.*/s.*/n)"), "lolbin_abuse",
    true(), NULL
)
| where isnotnull(technique)
| bin _time span=1h
| stats dc(technique) as technique_count values(technique) as techniques by host _time
| where technique_count >= 3
| sort - technique_count

关键概念

术语	定义
防御规避（TA0005）	MITRE ATT&CK 战术，指攻击者在行动过程中试图避免被检测
进程注入（T1055）	将代码注入另一个进程的内存空间，以在受信任上下文中执行的技术
时间戳篡改（T1070.006）	修改文件时间戳，使恶意文件看起来较旧并与合法文件混在一起
伪装（T1036）	将恶意文件或进程命名为与合法系统文件相同，以避免被检测
LOLBin	离地攻击二进制；被攻击者重新利用的合法 Windows 工具
指标清除（T1070）	清除日志、删除文件或修改痕迹，以移除失陷证据

工具与系统

• Sysmon：具有内核级可见性的高级 Windows 系统监控
• Microsoft Defender for Endpoint：具备高级搜寻（KQL）的 EDR，用于规避检测
• CrowdStrike Falcon：基于 IOA 的行为检测，用于规避技术
• Elastic Security：为 ATT&CK 规避技术提供预构建检测规则的 SIEM
• Sigma Rules：厂商无关的检测规则格式，具有广泛的规避规则库

常见陷阱

• 进程注入规则导致告警疲劳：许多合法工具（AV、辅助功能）会执行进程注入。维护一份已知良好源进程的允许列表。
• 遗漏 Sysmon 事件 ID 8/10：默认 Sysmon 配置可能无法捕获 CreateRemoteThread 或 ProcessAccess。请使用全面的 Sysmon 配置。
• 忽略父进程上下文：来自 cmd.exe 的可疑命令行，只有在 cmd.exe 的父进程异常时才值得关注（例如，Excel 启动 cmd.exe）。
• 未跨事件类型进行关联：单个事件往往是良性的。将多个弱信号（进程创建 + 网络连接 + 文件创建）结合起来，以实现高置信度检测。