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Detection rules › YARA-L

Potential Credential Dumping Via LSASS SilentProcessExit Technique

Severity
critical
Type
Detection
Time window
5m
Match by
hostname
Author
Florian Roth (Nextron Systems)
Source
github.com/chronicle/detection-rules

Detects changes to the Registry in which a monitor program gets registered to dump the memory of the lsass.exe process

Known false positives

  • Unlikely

MITRE ATT&CK coverage

TacticTechniques
Credential Access

References

Telemetry coverage

ProviderRecord / event type
SysmonEvent ID 13: RegistryEvent (Value Set)
Security-AuditingEvent ID 4657: A registry value was modified.

Rule body

// Copyright 2025 Google LLC. Licensed under Apache-2.0.

rule potential_cred_dumping_via_lsass_silentprocessexit_technique {

  meta:
    author = "Florian Roth (Nextron Systems)"
    description = "Detects changes to the Registry in which a monitor program gets registered to dump the memory of the lsass.exe process"
    reference = "https://github.com/SigmaHQ/sigma/blob/master/rules/windows/registry/registry_event/registry_event_silentprocessexit_lsass.yml"
    license = "https://github.com/SigmaHQ/Detection-Rule-License/blob/main/LICENSE.Detection.Rules.md"
    rule_name = "Potential Credential Dumping Via LSASS SilentProcessExit Technique"
    sigma_uuid = "55e29995-75e7-451a-bef0-6225e2f13597"
    sigma_status = "test"
    rule_id = "mr_bc2279f0-9b27-485d-b392-ff6f13ae68df"
    tactic = "TA0006"
    technique = "T1003.001"
    type = "Detection"
    data_source = "Sysmon"
    platform = "Windows"
    severity = "Critical"
    priority = "Critical"
    false_positives = "Unlikely"

  events:
    $registry.metadata.event_type = "REGISTRY_MODIFICATION"
    //$registry.metadata.product_event_type = "13"
    strings.contains(strings.to_lower($registry.target.registry.registry_key), "microsoft\\windows nt\\currentversion\\silentprocessexit\\lsass.exe")

    $registry.principal.hostname = $hostname

  match:
    $hostname over 5m

  outcome:
    //example usage of specifying test user and hostname to adjust risk score
    $risk_score = max(if($registry.principal.user.userid = "user" and $registry.principal.hostname = "hostname", 0, 15))
    $principal_hostname = array_distinct($registry.principal.hostname)
    $principal_process_pid = array_distinct($registry.principal.process.pid)
    $principal_process_file_full_path = array_distinct($registry.principal.process.file.full_path)
    $principal_process_product_specific_process_id = array_distinct($registry.principal.process.product_specific_process_id)
    $principal_user_userid = array_distinct($registry.principal.user.userid)
    $target_registry_key = array_distinct($registry.target.registry.registry_key)
    $target_registry_value = array_distinct($registry.target.registry.registry_value_data)

  condition:
    $registry
}

YARA-L rule structure

Condition

Fires when at least one $registry event in the 5m window.

Events

$registry REGISTRY_MODIFICATION (13, 4657)

  • target.registry.registry_key contains "microsoft\\windows nt\\currentversion\\silentprocessexit\\lsass.exe"

Match and correlation

Match key
$hostname (principal.hostname)
Within
5m

Outcome

Outcome variables add context to a detection. When the rule generates an alert, $risk_score is displayed with it.

FieldExpression
risk_scoremax(if($registry.principal.user.userid = "user" and $registry.principal.hostname = "hostname", 0, 15))
principal_hostnamearray_distinct($registry.principal.hostname)
principal_process_pidarray_distinct($registry.principal.process.pid)
principal_process_file_full_patharray_distinct($registry.principal.process.file.full_path)
principal_process_product_specific_process_idarray_distinct($registry.principal.process.product_specific_process_id)
principal_user_useridarray_distinct($registry.principal.user.userid)
target_registry_keyarray_distinct($registry.target.registry.registry_key)
target_registry_valuearray_distinct($registry.target.registry.registry_value_data)