Windows Visual Basic Commandline Compiler DNSQuery

name: Windows Visual Basic Commandline Compiler DNSQuery
id: 8976744a-ae7a-46a4-8128-690df85c2af4
version: 6
creation_date: '2025-08-28'
modification_date: '2026-05-13'
author: Teoderick Contreras, Splunk
status: production
type: TTP
description: The following analytic detects instances where vbc.exe, the Visual Basic Command Line Compiler, initiates DNS queries. Normally, vbc.exe operates locally to compile Visual Basic code and does not require internet access or to perform DNS lookups. Therefore, any observed DNS activity originating from vbc.exe is highly suspicious and indicative of potential malicious activity. This behavior often suggests that a malicious payload is masquerading as the legitimate vbc.exe process to establish command-and-control (C2) communication, resolve domains for data exfiltration, or download additional stages of malware. Security teams should investigate the process's parent, command-line arguments, and the resolved domains for further indicators of compromise.
data_source:
    - Sysmon EventID 22
search: |-
    `sysmon` EventCode=22 process_name="vbc.exe"
      | rename dvc as dest
      | stats count min(_time) as firstTime max(_time) as lastTime
        BY answer answer_count dest
           process_exec process_guid process_name
           query query_count reply_code_id
           signature signature_id src
           user_id vendor_product QueryName
           QueryResults QueryStatus
      | `security_content_ctime(firstTime)`
      | `security_content_ctime(lastTime)`
      | `windows_visual_basic_commandline_compiler_dnsquery_filter`
how_to_implement: To successfully implement this search, you need to be ingesting logs with the process name and eventcode = 22 dnsquery executions from your endpoints. If you are using Sysmon, you must have at least version 6.0.4 of the Sysmon TA. Tune and filter known instances where renamed rundll32.exe may be used.
known_false_positives: No false positives have been identified at this time.
references:
    - https://www.cisa.gov/news-events/cybersecurity-advisories/aa20-266a
drilldown_searches:
    - name: View the detection results for - "$dest$"
      search: '%original_detection_search% | search  dest = "$dest$"'
      earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
    - name: View risk events for the last 7 days for - "$dest$"
      search: '| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$dest$") | stats count min(_time) as firstTime max(_time) as lastTime values(search_name) as "Search Name" values(risk_message) as "Risk Message" values(analyticstories) as "Analytic Stories" values(annotations._all) as "Annotations" values(annotations.mitre_attack.mitre_tactic) as "ATT&CK Tactics" by normalized_risk_object | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`'
      earliest_offset: 7d
      latest_offset: "0"
finding:
    title: vbc.exe process [$process_name$] made a DNS query for $query$ from host $dest$.
    entity:
        field: dest
        type: system
        score: 50
threat_objects:
    - field: process_name
      type: process_name
analytic_story:
    - Lokibot
asset_type: Endpoint
mitre_attack_id:
    - T1071.004
product:
    - Splunk Enterprise
    - Splunk Enterprise Security
    - Splunk Cloud
category: endpoint
security_domain: endpoint
tests:
    - name: True Positive Test
      attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1071.004/vbc_dnsquery/vbc_dns_query.log
          source: XmlWinEventLog:Microsoft-Windows-Sysmon/Operational
          sourcetype: XmlWinEventLog
      test_type: unit