Sdiagnhost Calling Suspicious Child Process

Severity: high
Author: Nextron Systems, @Kostastsale
Source: upstream

Detects sdiagnhost.exe calling a suspicious child process (e.g. used in exploits for Follina / CVE-2022-30190)

MITRE ATT&CK coverage

Tactic	Techniques
Defense Evasion	`T1036` Masquerading, `T1218` System Binary Proxy Execution

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`

or:
Image|endswith: '\calc.exe'
Image|endswith: '\cmd.exe'
Image|endswith: '\cscript.exe'
Image|endswith: '\mshta.exe'
Image|endswith: '\powershell.exe'
Image|endswith: '\pwsh.exe'
Image|endswith: '\regsvr32.exe'
Image|endswith: '\rundll32.exe'
Image|endswith: '\taskkill.exe'
Image|endswith: '\wscript.exe'
ParentImage|endswith: '\sdiagnhost.exe'

Stage 2: `not 1 of filter_main_*`

or:
or:
CommandLine|endswith: '-noprofile -'
CommandLine|endswith: -noprofile
Image|endswith: '\powershell.exe'
CommandLine|contains: bits
Image|endswith: '\cmd.exe'

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`	ends_with	`-noprofile` `-noprofile -`
`CommandLine`	match	`bits`
`Image`	ends_with	`\calc.exe` corpus 13 (sigma 13) `\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) `\regsvr32.exe` corpus 57 (sigma 57) `\rundll32.exe` corpus 76 (sigma 76) `\taskkill.exe` corpus 2 (sigma 2) `\wscript.exe` corpus 64 (sigma 64)
`ParentImage`	ends_with	`\sdiagnhost.exe`