Local Accounts Discovery

/*
 * Copyright 2025 Google LLC
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

rule local_accounts_discovery {

  meta:
    author = "Timur Zinniatullin, Daniil Yugoslavskiy, oscd.community"
    description = "Local accounts, System Owner/User discovery using operating systems utilities"
    reference = "https://github.com/SigmaHQ/sigma/blob/master/rules/windows/process_creation/proc_creation_win_susp_local_system_owner_account_discovery.yml"
    license = "https://github.com/SigmaHQ/Detection-Rule-License/blob/main/LICENSE.Detection.Rules.md"
    rule_name = "Local Accounts Discovery"
    sigma_uuid = "502b42de-4306-40b4-9596-6f590c81f073"
    sigma_status = "test"
    rule_id = "mr_3a6b5c72-8126-4f43-a4ac-9c8bbac7fa72"
    tactic = "TA0007"
    technique = "T1033"
    type = "Detection"
    data_source = "Sysmon"
    platform = "Windows"
    severity = "Low"
    priority = "Low"
    false_positives = "Legitimate administrator or user enumerates local users for legitimate reason"

  events:
    $process.metadata.event_type = "PROCESS_LAUNCH"
    (
      (
        re.regex($process.target.process.file.full_path, `\\cmd\.exe$`) nocase and
        strings.contains(strings.to_lower($process.target.process.command_line), " /c") and
        strings.contains(strings.to_lower($process.target.process.command_line), "dir ") and
        strings.contains(strings.to_lower($process.target.process.command_line), "\\users\\") and
        NOT strings.contains(strings.to_lower($process.target.process.command_line), " rmdir ")
      )
      or
      (
        re.regex($process.target.process.file.full_path, `\\net\.exe$`) nocase or
        re.regex($process.target.process.file.full_path, `\\net1\.exe$`) nocase and
        strings.contains(strings.to_lower($process.target.process.command_line), "user") and
        NOT strings.contains(strings.to_lower($process.target.process.command_line), "/domain") and
        NOT strings.contains(strings.to_lower($process.target.process.command_line), "/add") and
        NOT strings.contains(strings.to_lower($process.target.process.command_line), "/delete") and
        NOT strings.contains(strings.to_lower($process.target.process.command_line), "/active") and
        NOT strings.contains(strings.to_lower($process.target.process.command_line), "/expires") and
        NOT strings.contains(strings.to_lower($process.target.process.command_line), "/passwordreq") and
        NOT strings.contains(strings.to_lower($process.target.process.command_line), "/scriptpath") and
        NOT strings.contains(strings.to_lower($process.target.process.command_line), "/times") and
        NOT strings.contains(strings.to_lower($process.target.process.command_line), "/workstations")
      )
      or
      (
        re.regex($process.target.process.file.full_path, `\\whoami\.exe$`) nocase or
        re.regex($process.target.process.file.full_path, `\\quser\.exe$`) nocase or
        re.regex($process.target.process.file.full_path, `\\qwinsta\.exe$`) nocase or
        (
          re.regex($process.target.process.file.full_path, `\\wmic\.exe$`) nocase and
          strings.contains(strings.to_lower($process.target.process.command_line), "useraccount") and
          strings.contains(strings.to_lower($process.target.process.command_line), "get")
        ) or
        (
          re.regex($process.target.process.file.full_path, `\\cmdkey\.exe$`) nocase and
          strings.contains(strings.to_lower($process.target.process.command_line), " /l")
        )
      )
    )
    $process.principal.hostname = $hostname

  match:
    $hostname over 5m

  outcome:
    //example usage of specifying test user and hostname to adjust risk score
    $risk_score = max(if($process.principal.user.userid = "user" and $process.principal.hostname = "hostname", 0, 15))
    $principal_process_pid = array_distinct($process.principal.process.pid)
    $principal_process_command_line = array_distinct($process.principal.process.command_line)
    $principal_process_file_sha256 = array_distinct($process.principal.process.file.sha256)
    $principal_process_file_full_path = array_distinct($process.principal.process.file.full_path)
    $principal_process_product_specfic_process_id = array_distinct($process.principal.process.product_specific_process_id)
    $principal_process_parent_process_product_specfic_process_id = array_distinct($process.principal.process.parent_process.product_specific_process_id)
    $target_process_pid = array_distinct($process.target.process.pid)
    $target_process_command_line = array_distinct($process.target.process.command_line)
    $target_process_file_sha256 = array_distinct($process.target.process.file.sha256)
    $target_process_file_full_path = array_distinct($process.target.process.file.full_path)
    $target_process_product_specfic_process_id = array_distinct($process.target.process.product_specific_process_id)
    $principal_user_userid = array_distinct($process.principal.user.userid)
    $log_type = array_distinct(strings.concat($process.metadata.log_type,"/",$process.metadata.product_event_type))

  condition:
    $process
}