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Default ACLs on Windows Event Logs

  • Articolo

A question I get asked frequently: what are the default ACLs on Windows event logs?

Here's the answer, straight from the source code with only a little formatting help from me, and in more detail than you probably care to know.

Windows 2000:

Application Event Log and custom event logs

ACE Type Principal Accesses
------------ ------------------ ------------
*Deny Anonymous All Access
*Deny Guests All Access
Allow LocalSystem Full Control
Allow Administrators Read, Clear
Allow Backup Operators Backup
Allow Server Operators Read, Clear
Allow Everyone Read
Allow Administrators Write
Allow Server Operators Write
Allow Everyone Write

* only if RestrictGuestAccess is set for this log

System Event Log

ACE Type Principal Accesses
------------ ------------------ ------------
*Deny Anonymous All Access
*Deny Guests All Access
Allow LocalSystem Full Control
Allow Administrators Read, Clear
Allow Backup Operators Backup
Allow Server Operators Read, Clear
Allow Everyone Read
Allow Administrators Write

* only if RestrictGuestAccess is set for this log

Security Event Log

ACE Type Principal Accesses
------------ ------------------ ------------
*Deny Anonymous All Access
*Deny Guests All Access

Allow LocalSystem Full Control
Allow Administrators Read, Clear

* only if RestrictGuestAccess is set for this log

Access to the security event log is governed by SeSecurityPrivilege (aka "Manage Audit and Security Log"). Holders of the privilege have Read, Clear, and Backup permission. Holders of SeAuditPrivilege (aka "Generate Security Audit") can write to the log via internal LSA APIs only. LocalSystem can write to the security event log via the ReportEvent API due to permission granted via the log ACL.

By default, these are the privilege assignments:

SeSecurityPrivilege Administrators, LocalSystem
SeAuditPrivilege LocalSystem

Windows XP with Service Pack 2:

Application Event Log and custom event logs

   ACE Type Principal Accesses
------------ ------------------ ------------
*Deny Anonymous All Access
*Deny Guests All Access
   Allow LocalSystem Full Control
Allow Administrators Read, Clear
Allow Backup Operators Backup
Allow Server Operators Read, Clear
Allow Everyone Read
Allow Administrators Write
Allow LocalService Write
Allow NetworkService Write
Allow Server Operators Write
Allow Everyone Write

* only if RestrictGuestAccess is set for this log

System Event Log

   ACE Type Principal Accesses
------------ ------------------ ------------
*Deny Anonymous All Access
*Deny Guests All Access
Allow LocalSystem Full Control
Allow Administrators Read, Clear
Allow Backup Operators Backup
Allow Server Operators Read, Clear
Allow Everyone Read
Allow Administrators Write
Allow LocalService Write
Allow NetworkService Write

* only if RestrictGuestAccess is set for this log

Security Event Log

ACE Type Principal Accesses
------------ ------------------ ------------
*Deny Anonymous All Access
*Deny Guests All Access

Allow LocalSystem Full Control
Allow Administrators Read, Clear

* only if RestrictGuestAccess is set for this log

Access to the security event log is governed by SeSecurityPrivilege (aka "Manage Audit and Security Log"). Holders of the privilege have Read, Clear, and Backup permission. Holders of SeAuditPrivilege (aka "Generate Security Audit") can write to the log via internal LSA APIs only. LocalSystem can not write to the security event log via the ReportEvent API regardless of permission.

By default, these are the privilege assignments:

SeSecurityPrivilege Administrators, LocalSystem
SeAuditPrivilege LocalService, NetworkService,
LocalSystem

Windows Server 2003:

Windows Server 2003 introduced configurable event log ACLs via the CustomSD registry value.

Here are the defaults, including the equivalent SDDL:

Application Event Log and custom event logs

O:BAG:SYD:
*(D;;0xf0007;;;AN) // (Deny) Anonymous:All Access
*(D;;0xf0007;;;BG) // (Deny) Guests:All Access
(A;;0xf0007;;;SY) // LocalSystem:Full
(A;;0x7;;;BA) // Administrators:Read,Write,Clear
(A;;0x7;;;SO) // Server Operators:Read,Write,Clear
(A;;0x3;;;IU) // INTERACTIVE LOGON:Read,Write
(A;;0x3;;;SU) // SERVICES LOGON:Read,Write
(A;;0x3;;;S-1-5-3) // BATCH LOGON:Read,Write

* only if RestrictGuestAccess is set for this log

System Event Log

O:BAG:SYD:
*(D;;0xf0007;;;AN) // (Deny) Anonymous:All Access
*(D;;0xf0007;;;BG) // (Deny) Guests:All Access
(A;;0xf0007;;;SY) // LocalSystem:Full
(A;;0x7;;;BA) // Administrators:Read,Write,Clear
(A;;0x5;;;SO) // Server Operators:Read,Clear
(A;;0x1;;;IU) // INTERACTIVE LOGON:Read
(A;;0x1;;;SU) // SERVICES LOGON:Read
(A;;0x1;;;S-1-5-3) // BATCH LOGON:Read
(A;;0x2;;;LS) // LocalService:Write
(A;;0x2;;;NS) // NetworkService:Write

* only if RestrictGuestAccess is set for this log

Security Event Log

O:BAG:SYD:
*(D;;0xf0007;;;AN) // (Deny) Anonymous:All Access
*(D;;0xf0007;;;BG) // (Deny) Guests:All Access
(A;;0xf0007;;;SY) // LocalSystem:Full
(A;;0x7;;;BA) // Administrators:Read,Write**,Clear

As with Windows XP and Windows 2000, privilege also allows access to the security log. SeSecurityPrivilege allows Read and Clear access to the security event log.

* only if RestrictGuestAccess is set for this log
** Regardless of permissions in the security event log ACL, SeAuditPrivilege is required to write to the security event log, and all writes can only occur via audit APIs (e.g. AuthzReportSecurityEvent), not through event log APIs (e.g. ReportEvent).

Starting with Windows Vista, you can actually enumerate the ACL on any log with the WEVTUTIL.EXE utility (running in an Administrator command prompt). As always, posession of SeAuditPrivilege allows write to the security event log regardless of ACL, and posession of SeSecurityPrivilege allows read and clear of the security event log regardless of ACL.

Windows Vista, Windows 7, Windows Server 2008, Windows Server 2008 R2, and beyond:

C:\Windows\system32>wevtutil gl security
name: security
enabled: true
type: Admin
owningPublisher:
isolation: Custom
channelAccess: O:BAG:SYD:(A;;CCLCSDRCWDWO;;;SY)(A;;CCLC;;;BA)(A;;CC;;;ER)
logging:
logFileName: %SystemRoot%\System32\Winevt\Logs\security.evtx
retention: false
autoBackup: false
maxSize: 786432000
publishing:
fileMax: 1

UPDATE 2006-03-07 - Added hyperlink to SDDL description

UPDATE 2011-05-24 - Added information for post-WS03 releases

Comments

  • Anonymous
    March 01, 2006
    Note to self: Eric has a good post about the default ACLs on the Windows event log, as taken directly from the source code. Included is the Windows Server 2003 defaults, including the equivalent SDDL. Useful information to compare to my hardening code

  • Anonymous
    March 05, 2006
    Eric Fitz took the trouble to search the Windows sources for default access control lists of the various event logs. He posted his findings for Windows 2000, XP with Service Pack 2 and Windows Server 2003 in the Windows Auditing...

  • Anonymous
    May 24, 2011
    What about windows 2008?

  • Anonymous
    May 24, 2011
    Hi Fred, Updated.