Suspicious Desktopimgdownldr Command

Severity: high
Author: Florian Roth (Nextron Systems)
Source: upstream

Detects a suspicious Microsoft desktopimgdownldr execution with parameters used to download files from the Internet

MITRE ATT&CK coverage

Tactic	Techniques
Command & Control	`T1105` Ingress Tool Transfer

Event coverage

Provider	Event ID	Title
Sysmon	1	Process creation
Security-Auditing	4688	A new process has been created.

Stages and Predicates

Stage 1: `selection1`

CommandLine|contains: ' /lockscreenurl:'

Stage 2: `not selection1_filter`

or:
CommandLine|contains: .jpeg
CommandLine|contains: .jpg
CommandLine|contains: .png

Stage 3: `selection_reg`

CommandLine|contains: '\PersonalizationCSP'
CommandLine|contains: 'reg delete'

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

Field	Kind	Values
`CommandLine`	match	`/lockscreenurl:` `.jpeg` corpus 6 (sigma 6) `.jpg` corpus 7 (sigma 7) `.png` corpus 7 (sigma 7) `\PersonalizationCSP` `reg delete`