Windows Management Instrumentation Event Subscription

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Windows Management Instrumentation Event Subscription
Technique
ID T1084
Tactic Persistence
Platform Windows Server 2003, Windows Server 2008, Windows Server 2012, Windows XP, Windows 7, Windows 8, Windows Server 2003 R2, Windows Server 2008 R2, Windows Server 2012 R2, Windows Vista, Windows 8.1
Permissions Required Administrator, SYSTEM
Data Sources WMI Objects

Windows Management Instrumentation (WMI) can be used to install event filters, providers, consumers, and bindings that execute code when a defined event occurs. Adversaries may use the capabilities of WMI to subscribe to an event and execute arbitrary code when that event occurs, providing persistence on a system. Adversaries may attempt to evade detection of this technique by compiling WMI scripts.1 Examples of events that may be subscribed to are the wall clock time or the computer's uptime.2 Several threat groups have reportedly used this technique to maintain persistence.3

Examples

  • APT29 has used WMI event filters to establish persistence.4
  • SeaDuke uses an event filter in WMI code to execute a previously dropped executable shortly after system startup.5

Mitigation

Disabling WMI services may cause system instability and should be evaluated to assess the impact to a network. By default, only administrators are allowed to connect remotely using WMI; restrict other users that are allowed to connect, or disallow all users from connecting remotely to WMI. Prevent credential overlap across systems of administrator and privileged accounts.5

Detection

Monitor WMI event subscription entries, comparing current WMI event subscriptions to known good subscriptions for each host. Tools such as Sysinternals Autoruns may also be used to detect WMI changes that could be attempts at persistence.6