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Detection rules › Sigma

Potential Ransomware Activity Using LegalNotice Message

Severity
high
Author
frack113
Source
upstream

Detect changes to the "LegalNoticeCaption" or "LegalNoticeText" registry values where the message set contains keywords often used in ransomware ransom messages

MITRE ATT&CK coverage

TacticTechniques
ImpactT1491.001 Defacement: Internal Defacement

Event coverage

ProviderEvent IDTitle
Sysmon13RegistryEvent (Value Set)

Stages and Predicates

Stage 1: selection

or:
Details|contains: Unlock-Password
Details|contains: encrypted
Details|contains: paying
or:
TargetObject|contains: '\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System\LegalNoticeCaption'
TargetObject|contains: '\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System\LegalNoticeText'

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.

FieldKindValues
Detailsmatch
  • Unlock-Password
  • encrypted
  • paying
TargetObjectmatch
  • \SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System\LegalNoticeCaption
  • \SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System\LegalNoticeText