Potential Ransomware or Unauthorized MBR Tampering Via Bcdedit.EXE

Severity: medium
Author: @neu5ron
Source: upstream

Detects potential malicious and unauthorized usage of bcdedit.exe

MITRE ATT&CK coverage

Tactic	Techniques
Persistence	`T1542.003` Pre-OS Boot: Bootkit
Defense Evasion	`T1070` Indicator Removal, `T1542.003` Pre-OS Boot: Bootkit

Event coverage

Provider	Event ID	Title
Sysmon	1	Process creation

Stages and Predicates

Stage 1: `all of selection_img`

or:
Image|endswith: '\bcdedit.exe'
OriginalFileName: bcdedit.exe

Stage 2: `all of selection_cli`

or:
CommandLine|contains: delete
CommandLine|contains: deletevalue
CommandLine|contains: import
CommandLine|contains: network
CommandLine|contains: safeboot

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`	match	`delete` corpus 7 (sigma 7) `deletevalue` `import` corpus 2 (sigma 2) `network` `safeboot`
`Image`	ends_with	`\bcdedit.exe` corpus 4 (sigma 4)
`OriginalFileName`	eq	`bcdedit.exe` corpus 2 (sigma 2)