GCTI Remote Access Tools

/*
 * 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 gcti_remote_access_tools {

  meta:
    author = "Google Cloud Security"
    description = "Alert process and file create events that are associated with hashes from the GCTI Remote Access Tool list"
    rule_id = "mr_d838d64d-4a6f-4999-a895-0b5771d02aa6"
    rule_name = "GCTI Remote Access Tools"
    tactic = "TA0011"
    technique = "T1219"
    type = "alert"
    tags = "rat"
    data_source = "crowdstrike, microsoft sysmon, microsoft defender atp"
    severity = "High"
    priority = "High"

    events:
    // find a process launch event
    ($process.metadata.event_type = "PROCESS_LAUNCH" or $process.metadata.event_type = "PROCESS_MODULE_LOAD" or $process.metadata.event_type = "PROCESS_UNCATEGORIZED" or $process.metadata.event_type = "FILE_CREATION")
    $process.target.process.file.sha256 != ""
    $process.target.process.file.sha256 = $rat_hash
    $process.principal.hostname = $hostname

    // join graph and event hashes
    $gcti.graph.entity.file.sha256 = $rat_hash

    // look for files identified as likely remote access tools
    $gcti.graph.metadata.entity_type = "FILE"
    $gcti.graph.metadata.vendor_name = "Google Cloud Threat Intelligence"
    $gcti.graph.metadata.product_name = "GCTI Feed"
    $gcti.graph.metadata.source_type = "GLOBAL_CONTEXT"
    $gcti.graph.metadata.threat.threat_feed_name = "Remote Access Tools"

  match:
    $hostname over 5m

  outcome:
    $risk_score = 65
    $event_count = count_distinct($process.metadata.id)
    // 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
    //$principal_hostname = array_distinct($process.principal.hostname)
    $principal_process_pid = array_distinct($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)
    $principal_process_product_specific_process_id = array_distinct($process.principal.process.product_specific_process_id)
    $principal_process_parent_process_product_specific_process_id = array_distinct($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)
    $target_process_product_specific_process_id = array_distinct($process.target.process.product_specific_process_id)
    $target_process_parent_process_product_specific_process_id = array_distinct($process.target.process.parent_process.product_specific_process_id)
    $target_file_full_path = array_distinct($process.target.file.full_path)
    $principal_user_userid = array_distinct($process.principal.user.userid)
    $target_resource_name = array_distinct($process.target.resource.name)

  condition:
    $process and $gcti
}