OneNote Attachment File Dropped In Suspicious Location

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

Detects creation of files with the ".one"/".onepkg" extension in suspicious or uncommon locations. This could be a sign of attackers abusing OneNote attachments

Event coverage

Provider	Event ID	Title
Sysmon	11	FileCreate

Stages and Predicates

Stage 1: `selection`

or:
TargetFilename|endswith: .one
TargetFilename|endswith: .onepkg
or:
TargetFilename|contains: ':\Temp\'
TargetFilename|contains: '\AppData\Local\Temp\'
TargetFilename|contains: '\Users\Public\'
TargetFilename|contains: '\Windows\Temp\'

Stage 2: `not 1 of filter_main_onenote`

Image|endswith: '\ONENOTE.EXE'
Image|contains: ':\Program Files\Microsoft Office\'

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	`\ONENOTE.EXE` corpus 3 (sigma 3)
`Image`	match	`:\Program Files\Microsoft Office\` corpus 4 (sigma 4)
`TargetFilename`	ends_with	`.one` `.onepkg`
`TargetFilename`	match	`:\Temp\` corpus 3 (sigma 3) `\AppData\Local\Temp\` corpus 11 (sigma 11) `\Users\Public\` corpus 2 (sigma 2) `\Windows\Temp\` corpus 3 (sigma 3)