DCOM InternetExplorer.Application Iertutil DLL Hijack - Security

Status: test
Severity: high
Log source: product windows, service security
Author: Roberto Rodriguez @Cyb3rWard0g, Open Threat Research (OTR)
Source: github.com/SigmaHQ/sigma

Detects a threat actor creating a file named iertutil.dll in the C:\Program Files\Internet Explorer\ directory over the network for a DCOM InternetExplorer DLL Hijack scenario.

MITRE ATT&CK coverage

Tactic	Techniques
Lateral Movement	`T1021.002` Remote Services: SMB/Windows Admin Shares `T1021.003` Remote Services: Distributed Component Object Model

Telemetry coverage

Provider	Record / event type
Security-Auditing	Event ID 5145: A network share object was checked to see whether client can be granted desired access.

Rule body

title: DCOM InternetExplorer.Application Iertutil DLL Hijack - Security
id: c39f0c81-7348-4965-ab27-2fde35a1b641
status: test
description: Detects a threat actor creating a file named `iertutil.dll` in the `C:\Program Files\Internet Explorer\` directory over the network for a DCOM InternetExplorer DLL Hijack scenario.
references:
    - https://threathunterplaybook.com/hunts/windows/201009-RemoteDCOMIErtUtilDLLHijack/notebook.html
author: Roberto Rodriguez @Cyb3rWard0g, Open Threat Research (OTR)
date: 2020-10-12
modified: 2022-11-26
tags:
    - attack.lateral-movement
    - attack.t1021.002
    - attack.t1021.003
logsource:
    product: windows
    service: security
detection:
    selection:
        EventID: 5145
        RelativeTargetName|endswith: '\Internet Explorer\iertutil.dll'
    filter:
        SubjectUserName|endswith: '$'
    condition: selection and not filter
falsepositives:
    - Unknown
level: high

Stages and Predicates

Stage 0: `condition`

selection and not filter

Stage 1: `selection`

selection:
    EventID: 5145
    RelativeTargetName|endswith: '\Internet Explorer\iertutil.dll'

Stage 2: `not filter`

filter:
    SubjectUserName|endswith: '$'

Exclusions

The rule actively suppresses these predicates.

Field	Kind	Excluded values	Search
`SubjectUserName`	ends_with	`$`	`excludes:SubjectUserName` `field:"SubjectUserName" value:"$"`

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`RelativeTargetName`	ends_with	`\Internet Explorer\iertutil.dll`	`field:"RelativeTargetName" kind:ends_with value:"\Internet Explorer\iertutil.dll"`