Suspicious Child Process of Notepad++ Updater - GUP.Exe

Severity: high
Author: Swachchhanda Shrawan Poudel (Nextron Systems)
Source: upstream

Detects suspicious child process creation by the Notepad++ updater process (gup.exe). This could indicate potential exploitation of the updater component to deliver unwanted malware.

MITRE ATT&CK coverage

Tactic	Techniques
Initial Access	`T1195.002` Supply Chain Compromise: Compromise Software Supply Chain
Credential Access	`T1557` Adversary-in-the-Middle
Collection	`T1557` Adversary-in-the-Middle

Event coverage

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

Stages and Predicates

Stage 1: `selection_parent`

ParentImage|endswith: '\gup.exe'

Stage 2: `1 of selection_child_img`

or:
Image|endswith: '\cmd.exe'
Image|endswith: '\cscript.exe'
Image|endswith: '\mshta.exe'
Image|endswith: '\powershell.exe'
Image|endswith: '\pwsh.exe'
Image|endswith: '\wscript.exe'

Stage 3: `1 of selection_child_cli`

or:
CommandLine|contains: bitsadmin
CommandLine|contains: certutil
CommandLine|contains: curl
CommandLine|contains: finger
CommandLine|contains: forfiles
CommandLine|contains: regsvr32
CommandLine|contains: rundll32
CommandLine|contains: wget

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	`bitsadmin` corpus 5 (sigma 5) `certutil` corpus 5 (sigma 5) `curl` corpus 3 (sigma 3) `finger` corpus 2 (sigma 2) `forfiles` corpus 2 (sigma 2) `regsvr32` corpus 11 (sigma 11) `rundll32` corpus 19 (sigma 19) `wget` corpus 2 (sigma 2)
`Image`	ends_with	`\cmd.exe` corpus 92 (sigma 92) `\cscript.exe` corpus 64 (sigma 64) `\mshta.exe` corpus 57 (sigma 57) `\powershell.exe` corpus 143 (sigma 143) `\pwsh.exe` corpus 140 (sigma 140) `\wscript.exe` corpus 64 (sigma 64)
`ParentImage`	ends_with	`\gup.exe` corpus 2 (sigma 2)

Neighbors

Stricter alternatives (narrower than this rule)

The rules below may be useful if you find the current rule is too noisy / lacks specificity.

Arbitrary Binary Execution Using GUP Utility [sigma] (adds 1 filter) (first-stage match only; downstream stages may differ)