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splunk-security_content/detections/endpoint/ssa___windows_mshta_inline_hta_execution.yml
2022-03-09 14:43:09 +01:00

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YAML

name: Windows MSHTA Inline HTA Execution
id: 24962154-9524-11ec-9333-acde48001122
version: 1
date: '2022-02-23'
author: Michael Haag, Splunk
type: TTP
datamodel:
- Endpoint_Processes
description: The following analytic identifies "mshta.exe" execution with inline protocol
handlers. "JavaScript", "VBScript", and "About" are the only supported options when
invoking HTA content directly on the command-line. The search will return the first
time and last time these command-line arguments were used for these executions,
as well as the target system, the user, process "mshta.exe" and its parent process.
search: '| from read_ssa_enriched_events() | eval timestamp=parse_long(ucast(map_get(input_event,
"_time"), "string", null)), cmd_line=lower(ucast(map_get(input_event, "process"),
"string", null)), process_name=lower(ucast(map_get(input_event, "process_name"),
"string", null)), process_path=ucast(map_get(input_event, "process_path"), "string",
null), parent_process_name=ucast(map_get(input_event, "parent_process_name"), "string",
null), event_id=ucast(map_get(input_event, "event_id"), "string", null) | where
cmd_line IS NOT NULL AND process_name IS NOT NULL | where process_name="mshta.exe"
AND (like (cmd_line, "%vbscript%") OR like (cmd_line, "%javascript%") OR like (cmd_line,
"%about%")) | eval start_time=timestamp, end_time=timestamp, entities=mvappend(ucast(map_get(input_event,
"dest_user_id"), "string", null), ucast(map_get(input_event, "dest_device_id"),
"string", null)), body=create_map(["event_id", event_id, "cmd_line", cmd_line, "process_name",
process_name, "parent_process_name", parent_process_name, "process_path", process_path])
| into write_ssa_detected_events();'
how_to_implement: To successfully implement this search you need to be ingesting information
on process that include the name of the process responsible for the changes from
your endpoints into the `Endpoint` datamodel in the `Processes` node. In addition,
confirm the latest CIM App 4.20 or higher is installed and the latest TA for the
endpoint product.
known_false_positives: Although unlikely, some legitimate applications may exhibit
this behavior, triggering a false positive.
references:
- https://github.com/redcanaryco/AtomicTestHarnesses
- https://redcanary.com/blog/introducing-atomictestharnesses/
- https://docs.microsoft.com/en-us/windows/win32/search/-search-3x-wds-extidx-prot-implementing
tags:
analytic_story:
- Suspicious MSHTA Activity
- Living Off The Land
cis20:
- CIS 8
confidence: 100
context:
- Source:Endpoint
- Stage:Defense Evasion
dataset:
- https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1218.005/atomic_red_team/windows-security.log
impact: 80
kill_chain_phases:
- Exploitation
message: An instance of $parent_process_name$ spawning $process_name$ was identified
on endpoint $dest_device_id$ by user $dest_user_id$ executing with inline HTA,
indicative of defense evasion.
mitre_attack_id:
- T1218.005
- T1218
nist:
- PR.PT
- DE.CM
observable:
- name: dest_user_id
type: User
role:
- Victim
- name: dest_device_id
type: Hostname
role:
- Victim
- name: parent_process_name
type: Process
role:
- Parent Process
- name: process_name
type: Process
role:
- Child Process
product:
- Splunk Behavioral Analytics
required_fields:
- _time
- dest_device_id
- process_name
- parent_process_name
- process_path
- dest_user_id
- process
- cmd_line
risk_score: 80
security_domain: endpoint
asset_type: Endpoint