Potentially Suspicious Child Process of KeyScrambler.exe

Severity: medium
Author: Swachchhanda Shrawan Poudel
Source: upstream

Detects potentially suspicious child processes of KeyScrambler.exe

MITRE ATT&CK coverage

Tactic	Techniques
Execution	`T1203` Exploitation for Client Execution
Persistence	`T1574.001` Hijack Execution Flow: DLL
Privilege Escalation	`T1574.001` Hijack Execution Flow: DLL
Defense Evasion	`T1574.001` Hijack Execution Flow: DLL

Event coverage

Provider	Event ID	Title
Sysmon	1	Process creation

Stages and Predicates

Stage 1: `all of selection_parent`

ParentImage|endswith: '\KeyScrambler.exe'

Stage 2: `all of selection_binaries`

or:
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: '\wscript.exe'
OriginalFileName: Cmd.Exe
OriginalFileName: PowerShell.EXE
OriginalFileName: RUNDLL32.EXE
OriginalFileName: cscript.exe
OriginalFileName: mshta.exe
OriginalFileName: pwsh.dll
OriginalFileName: regsvr32.exe
OriginalFileName: wscript.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
`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) `\regsvr32.exe` corpus 57 (sigma 57) `\rundll32.exe` corpus 76 (sigma 76) `\wscript.exe` corpus 64 (sigma 64)
`OriginalFileName`	eq	`Cmd.Exe` corpus 32 (sigma 30, splunk 2) `PowerShell.EXE` corpus 64 (sigma 60, splunk 4) `RUNDLL32.EXE` corpus 28 (sigma 25, splunk 3) `cscript.exe` corpus 15 (sigma 15) `mshta.exe` corpus 6 (sigma 6) `pwsh.dll` corpus 72 (sigma 68, splunk 4) `regsvr32.exe` corpus 4 (sigma 4) `wscript.exe` corpus 15 (sigma 15)
`ParentImage`	ends_with	`\KeyScrambler.exe`