Whoami Execution

/*
 * Copyright 2023 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 whoami_execution {

  meta:
    author = "Google Cloud Security"
    description = "Detects the execution of whoami, which is often used by attackers after exploitation to establish what credentials they are logged in under"
    rule_id = "mr_4372a068-1411-449f-b572-dc2b9358b5f4"
    rule_name = "Whoami Execution"
    type = "hunt"
    data_source = "microsoft sysmon, microsoft windows events"
    tactic = "TA0007"
    technique = "T1033"
    platform = "Windows"
    severity = "Info"
    priority = "Info"

  events:
    $process.metadata.event_type = "PROCESS_LAUNCH"
    $process.target.process.command_line = "whoami"

  outcome:
    $risk_score = 10
    // added to populate alert graph with additional context
    $principal_hostname = $process.principal.hostname
    $principal_process_pid = $process.principal.process.pid
    $principal_process_command_line = $process.principal.process.command_line
    $principal_process_file_sha256 = $process.principal.process.file.sha256
    $principal_process_file_full_path = $process.principal.process.file.full_path
    $principal_process_product_specific_process_id = $process.principal.process.product_specific_process_id
    $principal_process_parent_process_product_specific_process_id = $process.principal.process.parent_process.product_specific_process_id
    $target_process_pid = $process.target.process.pid
    $target_process_command_line = $process.target.process.command_line
    $target_process_file_sha256 = $process.target.process.file.sha256
    $target_process_file_full_path = $process.target.process.file.full_path
    $target_process_product_specific_process_id = $process.target.process.product_specific_process_id
    $principal_user_userid = $process.principal.user.userid

  condition:
    $process
}