Windows Visual Basic Commandline Compiler DNSQuery
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.
Query · spl
`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`
Implementation guide
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.
Analyst notes
Known false positives: No false positives have been identified at this time.