Renamed Office Binary Execution

Severity: high
Author: Nasreddine Bencherchali (Nextron Systems)
Source: upstream

Detects the execution of a renamed office binary

MITRE ATT&CK coverage

Tactic	Techniques
Defense Evasion	`T1036.003` Masquerading: Rename Legitimate Utilities

Event coverage

Provider	Event ID	Title
Sysmon	1	Process creation

Stages and Predicates

Stage 1: `selection`

or:
Description: 'Microsoft Access'
Description: 'Microsoft Excel'
Description: 'Microsoft OneNote'
Description: 'Microsoft Outlook'
Description: 'Microsoft PowerPoint'
Description: 'Microsoft Publisher'
Description: 'Microsoft Word'
Description: 'Sent to OneNote Tool'
OriginalFileName: Excel.exe
OriginalFileName: MSACCESS.EXE
OriginalFileName: MSPUB.EXE
OriginalFileName: OUTLOOK.EXE
OriginalFileName: Olk.exe
OriginalFileName: OneNote.exe
OriginalFileName: OneNoteM.exe
OriginalFileName: POWERPNT.EXE
OriginalFileName: WinWord.exe

Stage 2: `not 1 of filter_main_legit_names`

or:
Image|endswith: '\EXCEL.exe'
Image|endswith: '\MSACCESS.exe'
Image|endswith: '\MSPUB.EXE'
Image|endswith: '\OLK.EXE'
Image|endswith: '\ONENOTE.EXE'
Image|endswith: '\ONENOTEM.EXE'
Image|endswith: '\OUTLOOK.EXE'
Image|endswith: '\POWERPNT.EXE'
Image|endswith: '\WINWORD.exe'
Image|endswith: '\excelcnv.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
`Description`	eq	`Microsoft Access` `Microsoft Excel` `Microsoft OneNote` `Microsoft Outlook` `Microsoft PowerPoint` `Microsoft Publisher` `Microsoft Word` `Sent to OneNote Tool`
`Image`	ends_with	`\EXCEL.exe` corpus 2 (sigma 2) `\MSACCESS.exe` `\MSPUB.EXE` corpus 2 (sigma 2) `\OLK.EXE` `\ONENOTE.EXE` corpus 3 (sigma 3) `\ONENOTEM.EXE` `\OUTLOOK.EXE` corpus 3 (sigma 3) `\POWERPNT.EXE` corpus 4 (sigma 4) `\WINWORD.exe` corpus 5 (sigma 5) `\excelcnv.exe`
`OriginalFileName`	eq	`Excel.exe` corpus 3 (sigma 3) `MSACCESS.EXE` `MSPUB.EXE` `OUTLOOK.EXE` `Olk.exe` `OneNote.exe` `OneNoteM.exe` `POWERPNT.EXE` corpus 3 (sigma 3) `WinWord.exe` corpus 4 (sigma 4)