mirror of
https://github.com/splunk/security_content
synced 2026-06-08 17:32:49 +00:00
Bhavin Patel
76 lines
2.9 KiB
YAML
76 lines
2.9 KiB
YAML
name: PowerShell WebRequest Using Memory Stream
|
|
id: 103affa6-924a-4b53-aff4-1d5075342aab
|
|
version: 2
|
|
date: '2024-05-12'
|
|
author: Steven Dick
|
|
status: production
|
|
type: TTP
|
|
description: The following analytic detects the use of .NET classes in PowerShell
|
|
to download a URL payload directly into memory, a common fileless malware staging
|
|
technique. It leverages PowerShell Script Block Logging (EventCode=4104) to identify
|
|
suspicious PowerShell commands involving `system.net.webclient`, `system.net.webrequest`,
|
|
and `IO.MemoryStream`. This activity is significant as it indicates potential fileless
|
|
malware execution, which is harder to detect and can bypass traditional file-based
|
|
defenses. If confirmed malicious, this technique could allow attackers to execute
|
|
code in memory, evade detection, and maintain persistence in the environment.
|
|
data_source:
|
|
- Powershell Script Block Logging 4104
|
|
search: '`powershell` EventCode=4104 ScriptBlockText IN ("*system.net.webclient*","*system.net.webrequest*")
|
|
AND ScriptBlockText="*IO.MemoryStream*" | eval Path = case(isnotnull(Path),Path,true(),"unknown")
|
|
| stats count min(_time) as firstTime max(_time) as lastTime list(ScriptBlockText)
|
|
as command values(Path) as file_name values(UserID) as user by ActivityID, Computer,
|
|
EventCode | rename Computer as dest, EventCode as signature_id | `security_content_ctime(firstTime)`
|
|
| `security_content_ctime(lastTime)` | `powershell_webrequest_using_memory_stream_filter`'
|
|
how_to_implement: The following analytic requires PowerShell operational logs to be
|
|
imported. Modify the powershell macro as needed to match the sourcetype or add index.
|
|
This analytic is specific to 4104, or PowerShell Script Block Logging.
|
|
known_false_positives: Unknown, possible custom scripting.
|
|
references:
|
|
- https://www.mandiant.com/resources/blog/tracking-evolution-gootloader-operations
|
|
- https://thedfirreport.com/2022/05/09/seo-poisoning-a-gootloader-story/
|
|
- https://attack.mitre.org/techniques/T1059/001/
|
|
tags:
|
|
analytic_story:
|
|
- Malicious PowerShell
|
|
asset_type: Endpoint
|
|
confidence: 80
|
|
impact: 100
|
|
message: Powershell webrequest to memory stream behavior. Possible fileless malware
|
|
staging on $dest$ by $user$.
|
|
mitre_attack_id:
|
|
- T1059.001
|
|
- T1105
|
|
- T1027.011
|
|
observable:
|
|
- name: dest
|
|
type: Endpoint
|
|
role:
|
|
- Victim
|
|
- name: user
|
|
type: User
|
|
role:
|
|
- Victim
|
|
- name: file_name
|
|
type: File Name
|
|
role:
|
|
- Attacker
|
|
product:
|
|
- Splunk Enterprise
|
|
- Splunk Enterprise Security
|
|
- Splunk Cloud
|
|
required_fields:
|
|
- _time
|
|
- EventCode
|
|
- ActivityID
|
|
- Computer
|
|
- ScriptBlockText
|
|
risk_score: 80
|
|
security_domain: endpoint
|
|
tests:
|
|
- name: True Positive Test
|
|
attack_data:
|
|
- data:
|
|
https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/malware/gootloader/partial_ttps/windows-powershell-xml.log
|
|
source: XmlWinEventLog:Microsoft-Windows-PowerShell/Operational
|
|
sourcetype: XmlWinEventLog
|