Windows Shell/Scripting Application File Write to Suspicious Folder

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

Detects Windows shells and scripting applications that write files to suspicious folders

MITRE ATT&CK coverage

Tactic	Techniques
Execution	`T1059` Command and Scripting Interpreter

Event coverage

Provider	Event ID	Title
Sysmon	11	FileCreate

Stages and Predicates

Stage 1: `1 of selection_1`

or:
Image|endswith: '\bash.exe'
Image|endswith: '\cmd.exe'
Image|endswith: '\cscript.exe'
Image|endswith: '\msbuild.exe'
Image|endswith: '\powershell.exe'
Image|endswith: '\pwsh.exe'
Image|endswith: '\sh.exe'
Image|endswith: '\wscript.exe'
or:
TargetFilename|startswith: 'C:\PerfLogs\'
TargetFilename|startswith: 'C:\Users\Public\'

Stage 2: `1 of selection_2`

or:
Image|endswith: '\certutil.exe'
Image|endswith: '\forfiles.exe'
Image|endswith: '\mshta.exe'
Image|endswith: '\schtasks.exe'
Image|endswith: '\scriptrunner.exe'
Image|endswith: '\wmic.exe'
or:
TargetFilename|contains: 'C:\PerfLogs\'
TargetFilename|contains: 'C:\Users\Public\'
TargetFilename|contains: 'C:\Windows\Temp\'

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	`\bash.exe` corpus 17 (sigma 17) `\certutil.exe` corpus 34 (sigma 34) `\cmd.exe` corpus 92 (sigma 92) `\cscript.exe` corpus 64 (sigma 64) `\forfiles.exe` corpus 11 (sigma 11) `\msbuild.exe` corpus 7 (sigma 7) `\mshta.exe` corpus 57 (sigma 57) `\powershell.exe` corpus 143 (sigma 143) `\pwsh.exe` corpus 140 (sigma 140) `\schtasks.exe` corpus 45 (sigma 45) `\scriptrunner.exe` corpus 8 (sigma 8) `\sh.exe` corpus 13 (sigma 13) `\wmic.exe` corpus 37 (sigma 37) `\wscript.exe` corpus 64 (sigma 64)
`TargetFilename`	match	`C:\PerfLogs\` corpus 2 (sigma 2) `C:\Users\Public\` corpus 2 (sigma 2) `C:\Windows\Temp\`
`TargetFilename`	starts_with	`C:\PerfLogs\` corpus 2 (sigma 2) `C:\Users\Public\`