rw_windows_password_spray_T1110_003

rule rw_windows_password_spray_T1110_003 {

  meta:
    author = "Google Cloud Security"
    description = "Detect repeated authentication failure with multiple users indicative of a password spray attack."
    rule_id = "mr_5d6c9686-992f-4caf-bf1b-2fec05925c49"
    rule_name = "MITRE ATT&CK T1110.003 RW Windows Password Spray"
    type = "alert"
    data_source = "microsoft windows events"
    tactic = "TA0006"
    technique = "T1110.003"
    platform = "Windows"
    severity = "Medium"
    priority = "Medium"

  events:
    $login.metadata.event_type = "USER_LOGIN"
    $login.metadata.vendor_name = "Microsoft"
    $login.principal.hostname = $hostname
    $login.target.user.userid = $user
    $login.security_result.action = "BLOCK"

  match:
    $hostname over 30m

  outcome:
    $risk_score = 65
    $event_count = count_distinct($login.metadata.id)
    $user_login_threshold = 10
    $target_user_distinct_count = count_distinct($user)
    $target_user_count = count($user)
    $tlp = array_distinct("amber")
    // added to populate alert graph with additional context
    // Commented out principal.hostname because it is already represented in graph as match variable. If match changes, can uncomment to add to results
    //$principal_hostname = array_distinct($login.principal.hostname)
    $principal_ip = array_distinct($login.principal.ip)
    $target_hostname = array_distinct($login.target.hostname)
    $src_hostname = array_distinct($login.src.hostname)
    $target_ip = array_distinct($login.target.ip)
    $principal_user_userid = array_distinct($login.principal.user.userid)
    $target_user_userid = array_distinct($login.target.user.userid)
    $principal_resource_name = array_distinct($login.principal.resource.name)
    $target_resource_name = array_distinct($login.target.resource.name)
    $target_url = array_distinct($login.target.url)

  condition:
    #user > 10
}