analyzing-windows-event-logs-in-splunk

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• LICENSE
• SKILL.md
• api-reference.md · references/
• agent.py · scripts/

SKILL.md (first lines)

# Analyzing Windows Event Logs in Splunk

## When to Use

Use this skill when:
- SOC analysts investigate alerts related to Windows authentication, process execution, or AD changes
- Detection engineers build SPL queries for Windows-based threat detection
- Incident responders need forensic timelines of Windows endpoint or domain controller activity
- Periodic threat hunting targets Windows-specific ATT&CK techniques

**Do not use** for Linux/macOS endpoint analysis or network-only investigations.

## Prerequisites

- Splunk with Windows Event Log data ingested (sourcetype `WinEventLog:Security`, `WinEventLog:System`, `XmlWinEventLog:Microsoft-Windows-Sysmon/Operational`)
- Sysmon deployed on endpoints with SwiftOnSecurity or Olaf Hartong configuration
- CIM data model acceleration for Endpoint and Authentication data models
- Knowledge of Windows Security Event IDs and Sysmon event types

## Workflow

### Step 1: Authentication Attack Detection

**Brute Force Detection (EventCode 4625 — Failed Logon):**
```spl
index=wineventlog sourcetype="WinEventLog:Security" EventCode=4625
| stats count, dc(TargetUserName) AS unique_users, values(TargetUserName) AS targeted_users
  by src_ip, Logon_Type, Status
| where count > 20
| eval attack_type = case(
    Logon_Type=3, "Network Brute Force",
    Logon_Type=10, "RDP Brute Force",
    Logon_Type=2, "Interactive Brute Force",
    1=1, "Other"
  )
| eval status_meaning = case(
    Status="0xc000006d", "Bad Username or Password",
    Status="0xc000006a", "Incorrect Password (valid user)",
    Status="0xc0000234", "Account Locked Out",
    Status="0xc0000072", "Account Disabled",
    1=1, Status
  )
| sort - count
| table src_ip, attack_type, status_meaning, count, unique_users, targeted_users
```

**Password Spray Detection:**
```spl
index=wineventlog sourcetype="WinEventLog:Security" EventCode=4625 Logon_Type=3
| bin _time span=10m
| stats dc(TargetUserName) AS unique_users, count AS total_attempts,
  values(TargetUserName) AS users_targeted by src_ip, _time
| where unique_users > 10 AND total_attempts < unique_users * 3
| eval spray_confidence = if(unique_users > 25, "HIGH", "MEDIUM")
```

**Successful Logon After Failures (Compromise Indicator):**
```spl
index=wineventlog sourcetype="WinEventLog:Security"
(EventCode=4625 OR EventCode=4624) src_ip!="127.0.0.1"
| sort _time
| stats earliest(_time) AS first_seen, latest(_time) AS last_seen,
  sum(eval(if(EventCode=4625,1,0))) AS failures,
  sum(eval(if(EventCode=4624,1,0))) AS successes
  by src_ip, TargetUserName, ComputerName
| where failures > 10 AND successes > 0
| eval time_to_success = round((last_seen - first_seen)/60, 1)
| sort - failures
```

### Step 2: Privilege Escalation Detection

**New Admin Account Created (T1136.001):**
```spl
index=wineventlog sourcetype="WinEventLog:Security" EventCode=4720
| join TargetUserName type=left [
    search index=wineventlog EventCode=4732 TargetUserName="Administrators"
    | rename MemberName AS TargetUserName
  ]
| table _time, SubjectUserName, TargetUserName, ComputerName
| eval alert = "New account created and added to Administrators group"
```

**Special Privileges Assigned (EventCode 4672):**
```spl
index=wineventlog sourcetype="WinEventLog:Security" EventCode=4672
SubjectUserName!="SYSTEM" SubjectUserName!="LOCAL SERVICE" SubjectUserName!="NETWORK SERVICE"
| stats count, values(PrivilegeList) AS privileges by SubjectUserName, ComputerName
| where count > 0
| search privileges IN ("SeDebugPrivilege", "SeTcbPrivilege", "SeBackupPrivilege",
  "SeRestorePrivilege", "SeAssignPrimaryTokenPrivilege")
```

**Token Manipulation Detection (T1134):**
```spl
index=sysmon EventCode=10 TargetImage="*\\lsass.exe"
GrantedAccess IN ("0x1010", "0x1038", "0x1fffff", "0x40")
| stats count by SourceImage, SourceUser, Computer, GrantedAccess
| where NOT match(SourceImage, "(svchost|csrss|wininit|MsMpEng|CrowdStrike)")
| sort - count
```

### Step 3: Persistence Mechanism Detection

**Scheduled Task Creation (T1053.005):**
```spl
index=wineventlog (sourcetype="WinEventLog:Security" EventCode=4698)
  OR (sourcetype="XmlWinEventLog:Microsoft-Windows-Sysmon/Operational" EventCode=1
      Image="*\\schtasks.exe")
| eval task_info = coalesce(TaskContent, CommandLine)
| search task_info="*powershell*" OR task_info="*cmd*" OR task_info="*http*" OR task_info="*\\Temp\\*"
| table _time, Computer, SubjectUserName, TaskName, task_info
```

**Registry Run Key Modification (T1547.001):**
```spl
index=sysmon EventCode=13
TargetObject IN (
  "*\\CurrentVersion\\Run\\*",
  "*\\CurrentVersion\\RunOnce\\*",

From mukul975/Anthropic-Cybersecurity-Skills, Apache-2.0.

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