splunk-security_content/docs/_posts/2022-02-18-rundll32_dnsquery.md

title, excerpt, categories, last_modified_at, toc, toc_label, tags

title	excerpt	categories	last_modified_at	toc	toc_label	tags
Rundll32 DNSQuery	Signed Binary Proxy Execution, Rundll32	Endpoint	2022-02-18	true		Signed Binary Proxy Execution Defense Evasion Rundll32 Defense Evasion Splunk Enterprise Splunk Enterprise Security Splunk Cloud Endpoint

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Description

This search is to detect a suspicious rundll32.exe process having a http connection and do a dns query in some web domain. This technique was seen in IcedID malware where the rundll32 that execute its payload will contact amazon.com to check internet connect and to communicate to its C&C server to download config and other file component.

• Type: TTP
• Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
• Datamodel: Endpoint
• Last Updated: 2022-02-18
• Author: Teoderick Contreras, Splunk
• ID: f1483f5e-ee29-11eb-9d23-acde48001122

ATT&CK

ID	Technique	Tactic
T1218	Signed Binary Proxy Execution	Defense Evasion

| T1218.011 | Rundll32 | Defense Evasion |

Search

`sysmon` EventCode=22 process_name="rundll32.exe" 
| stats count min(_time) as firstTime max(_time) as lastTime by Image QueryName QueryStatus ProcessId  Computer 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| `rundll32_dnsquery_filter`

Macros

The SPL above uses the following Macros:

• security_content_ctime
• sysmon

Note that rundll32_dnsquery_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Required field

• _time
• Image
• QueryName
• QueryStatus
• ProcessId
• Computer

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

unknown

Associated Analytic story

• IcedID

Kill Chain Phase

• Exploitation

RBA

Risk Score	Impact	Confidence	Message
56.0	70	80	rundll32 process process_name having a dns query to QueryName in host Computer

Note that risk score is calculated base on the following formula: (Impact * Confidence)/100

Reference

• https://any.run/malware-trends/icedid

Test Dataset

Replay any dataset to Splunk Enterprise by using our replay.py tool or the UI. Alternatively you can replay a dataset into a Splunk Attack Range

• https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/malware/icedid/inf_icedid/windows-sysmon.log

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