Windows Event Log Storage Architecture: Forensic Analysis and PCI DSS Compliance for Win2000/2003 Server


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When dealing with legacy systems like Windows 2000 Server and Windows 2003 SP1, understanding event log storage is crucial for PCI DSS compliance. These versions use a proprietary binary format stored in:

%SystemRoot%\System32\config\
  - AppEvent.evt (Application logs)
  - SecEvent.evt (Security logs)
  - SysEvent.evt (System logs)

The .evt files use a fixed-length record structure with this approximate layout:

typedef struct _EVENTLOGRECORD {
  DWORD Length;
  DWORD Reserved;
  DWORD RecordNumber;
  DWORD TimeGenerated;
  DWORD TimeWritten;
  DWORD EventID;
  WORD EventType;
  WORD NumStrings;
  WORD EventCategory;
  WORD ReservedFlags;
  DWORD ClosingRecordNumber;
  DWORD StringOffset;
  DWORD UserSidLength;
  DWORD UserSidOffset;
  DWORD DataLength;
  DWORD DataOffset;
  // Variable data follows...
} EVENTLOGRECORD, *PEVENTLOGRECORD;

Financial systems logging sensitive data pose three critical challenges:

  • Residual data in slack space of .evt files
  • Potential credit card numbers in error messages
  • System-generated backups in %SystemRoot%\system32\config\*.evt

For programmatic cleaning, use the Windows Event Log API:

HANDLE hEventLog = OpenEventLog(NULL, "Application");
if (hEventLog) {
  if (!ClearEventLog(hEventLog, NULL)) {
    printf("Error clearing log: %d\n", GetLastError());
  }
  CloseEventLog(hEventLog);
}

For physical file sanitization (Windows 2003 SP1):

# PowerShell equivalent (where available)
wevtutil cl Application
wevtutil cl Security
wevtutil cl System

Create a custom VBScript for legacy systems:

Set objShell = CreateObject("WScript.Shell")
objShell.Run "cmd /c for %f in (%systemroot%\system32\config\*.evt) do cipher /w:%f", 0, True

Remember that Windows 2000 requires additional steps:

  1. Stop the EventLog service
  2. Delete all .evt files
  3. Run disk sanitization tools
  4. Reboot to regenerate clean logs

On Windows 2000 Server and 2003 SP1 systems, event logs are stored as proprietary binary files with the following characteristics:

Default locations:
- System: %SystemRoot%\System32\Config\SysEvent.Evt
- Application: %SystemRoot%\System32\Config\AppEvent.Evt
- Security: %SystemRoot%\System32\Config\SecEvent.Evt

The EVT file format uses a circular logging architecture with fixed record structures. Each log entry contains:

  • 4-byte record length header
  • 8-byte timestamp (FILETIME format)
  • 4-byte event ID
  • 2-byte event type
  • Variable-length strings for message components

When dealing with financial transaction logs under PCI DSS Requirement 3.2:

Key constraints:
- PAN (Primary Account Numbers) must not persist in logs beyond necessity
- Audit trails must maintain integrity during modification
- Clear documentation of log retention policies required

For Windows 2000/2003, the most reliable access methods are:

Option 1: Windows Event Log API

// C++ example using Win32 API
HANDLE hEventLog = OpenEventLog(NULL, "Application");
if (hEventLog != NULL) {
    EVENTLOGRECORD *pevlr;
    DWORD dwRead, dwNeeded;
    
    while(ReadEventLog(hEventLog, 
        EVENTLOG_SEQUENTIAL_READ | EVENTLOG_FORWARDS_READ,
        0, pevlr, BUFSIZ, &dwRead, &dwNeeded)) {
        
        // Process event records here
        printf("Event ID: %d\n", pevlr->EventID);
        
        // Zero out sensitive data if found
        if(pevlr->EventID == YOUR_FINANCIAL_EVENT_ID) {
            memset(pevlr + pevlr->DataOffset, 0, pevlr->DataLength);
        }
    }
    CloseEventLog(hEventLog);
}

Option 2: WMI Queries (Windows 2003)

# PowerShell 1.0 compatible script
$events = Get-WmiObject -Class Win32_NTLogEvent -Filter "LogFile='Application'"
foreach ($event in $events) {
    if ($event.EventCode -eq "1234") {
        # Create modified copy without sensitive data
        $cleanMessage = $event.Message -replace "\d{4}-\d{4}-\d{4}-\d{4}", "[PAN REDACTED]"
        
        # Write cleaned version to new log
        $event.Message = $cleanMessage
        $event.Put()
    }
}

For PCI-compliant log modification:

  1. Export original logs with wevtutil (2003):
    2. wevtutil epl Application application_backup.evtx
  2. Filter sensitive data using XPath:
    3. <QueryList>
  <Query Id="0" Path="Application">
    <Select Path="Application">*[System[EventID!=1234]]</Select>
  </Query>
</QueryList>
  3. Import cleaned data:
    4. wevtutil al application_clean.evtx /l:Application

For Windows 2000 limitations:

  • No native CLI tools - must use API programming
  • EVT files can become corrupted if modified directly
  • Consider redirecting logs to SQL Server using custom sinks

Always validate hash signatures (SHA-256) of modified logs and maintain chain-of-custody documentation for PCI auditors.