LoFP LoFP / modifications to appcertdll entries may be made by legitimate software updates or trusted system management tools. review changes to ensure they are from approved sources.

Techniques

Sample rules

Windows AppCertDLL Modification Via Registry

Description

This analytic detects attempts to modify AppCertDLL registry entries. Values under this registry entry are used to specify DLLs loaded by the Windows Session Manager. Such modifications can be abused by attackers to load malicious code early in the system startup process, enabling persistent malware execution with high privileges. If confirmed malicious, this behavior may lead to system compromise, persistence, and the evasion of security controls.

Detection logic


| tstats `security_content_summariesonly`
  count min(_time) as firstTime
        max(_time) as lastTime

FROM datamodel=Endpoint.Registry WHERE

Registry.action = "modified"
Registry.registry_path= "*\\Control\\Session Manager\\AppCertDLLs\\*"
Registry.registry_value_data = "*"

by Registry.action Registry.dest Registry.process_guid Registry.process_id
   Registry.registry_hive Registry.registry_path Registry.registry_key_name
   Registry.registry_value_data Registry.registry_value_name
   Registry.registry_value_type Registry.status
   Registry.user Registry.vendor_product


| `drop_dm_object_name(Registry)`

| where isnotnull(registry_value_data)

| `security_content_ctime(firstTime)`

| `security_content_ctime(lastTime)`

| `windows_appcertdll_modification_via_registry_filter`