Windows Management Instrumentation Event Subscription
Adversaries may establish persistence and elevate privileges by executing malicious content triggered by a Windows Management Instrumentation (WMI) event subscription. WMI can be used to install event filters, providers, consumers, and bindings that execute code when a defined event occurs. Examples of events that may be subscribed to are the wall clock time, user login, or the computer's uptime. 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 also compile WMI scripts – using `mofcomp.exe` –into Windows Management Object (MOF) files (.mof extension) that can be used to create a malicious subscription. WMI subscription execution is proxied by the WMI Provider Host process (WmiPrvSe.exe) and thus may result in elevated SYSTEM privileges.
Open detection, hunting, mitigation, and evidence workspace
Detection logic
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. Monitor for the creation of new WMI EventFilter, EventConsumer, and FilterToConsumerBinding events. Event ID 5861 is logged on Windows 10 systems when new EventFilterToConsumerBinding events are created. Monitor processes and command-line arguments that can be used to register WMI persistence, such as the Register-WmiEvent PowerShell cmdlet, as well as those that result from the execution of subscriptions (i.e. spawning from the WmiPrvSe.exe WMI Provider Host process).