Remote File Download Via Desktopimgdownldr Utility

Status: test
Severity: medium
Log source: category process_creation, product windows
Author: Tim Rauch, Elastic (idea)
Source: github.com/SigmaHQ/sigma

Detects the desktopimgdownldr utility being used to download a remote file. An adversary may use desktopimgdownldr to download arbitrary files as an alternative to certutil.

MITRE ATT&CK coverage

Tactic	Techniques
Command & Control	`T1105` Ingress Tool Transfer

Telemetry coverage

Provider	Record / event type
Sysmon	Event ID 1: Process creation
Security-Auditing	Event ID 4688: A new process has been created.

Rule body

title: Remote File Download Via Desktopimgdownldr Utility
id: 214641c2-c579-4ecb-8427-0cf19df6842e
status: test
description: Detects the desktopimgdownldr utility being used to download a remote file. An adversary may use desktopimgdownldr to download arbitrary files as an alternative to certutil.
references:
    - https://www.elastic.co/guide/en/security/current/remote-file-download-via-desktopimgdownldr-utility.html
author: Tim Rauch, Elastic (idea)
date: 2022-09-27
tags:
    - attack.command-and-control
    - attack.t1105
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith: '\desktopimgdownldr.exe'
        ParentImage|endswith: '\desktopimgdownldr.exe'
        CommandLine|contains: '/lockscreenurl:http'
    condition: selection
falsepositives:
    - Unknown
level: medium

Stages and Predicates

Stage 0: `condition`

selection

Stage 1: `selection`

selection:
    Image|endswith: '\desktopimgdownldr.exe'
    ParentImage|endswith: '\desktopimgdownldr.exe'
    CommandLine|contains: '/lockscreenurl:http'

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`CommandLine`	match	`/lockscreenurl:http`	`field:"CommandLine" kind:match value:"/lockscreenurl:http"`
`Image`	ends_with	`\desktopimgdownldr.exe` corpus 5 (sigma 5)	`field:"Image" kind:ends_with value:"\desktopimgdownldr.exe"`
`ParentImage`	ends_with	`\desktopimgdownldr.exe`	`field:"ParentImage" kind:ends_with value:"\desktopimgdownldr.exe"`