Blackbasta Registrydefaulticon

KQL detection rule by reversinglabs · MIT

Black Basta ransomware will create a new registry key to associate an icon with the .basta extension (V1), or the generated 9-character alphanumeric extension (V2) for encrypted files

// ATT&CK: T1112 - Modify Registry
// Description: Black Basta ransomware will create a new registry key to associate an icon with the .basta extension (V1), or the generated 9-character alphanumeric extension (V2) for encrypted files
SecurityEvent
| where EventID == 4657
| parse ObjectName with "\\REGISTRY\\" RegistryKey
| where RegistryKey has "\\Classess\\.basta\\DefaultIcon" or RegistryKey matches regex @"Classes\\[0-9a-zA-Z]{9}\\DefaultIcon"
| where NewValue == "%\\AppData\\Local\\Temp\\fkdjsadasd.ico"
| project TimeGenerated, Computer, RegistryKey, NewValue, OldValue, ProcessName, Account, Type
| union (DeviceRegistryEvents
| where ActionType == "RegistryValueSet"
| where RegistryKey has "\\Classes\\.basta\\DefaultIcon" or RegistryKey matches regex @"Classes\\[0-9a-zA-Z]{9}\\DefaultIcon"
| where RegistryValueData has "%\\AppData\\Local\\Temp\\fkdjsadasd.ico"
| project TimeGenerated=Timestamp, Computer=DeviceName, RegistryKey, RegistryValueName, NewValue=RegistryValueData, OldValue=PreviousRegistryValueData, Account=InitiatingProcessAccountName, InitiatingProcessId, InitiatingProcessCommandLine, InitiatingProcessSHA1, InitiatingProcessParentFileName, Type)

[[ currentRule.title && currentRule.title.length > 60 ? currentRule.title.slice(0, 60) + '…' : currentRule.title ]]

60b96cbb-38f5-4f92-a30c-1aabbe143cc8

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Executable code, not a declarative rule

This submission is arbitrary [[ currentRule.format ? currentRule.format.toUpperCase() : '' ]] code, not a declarative detection rule — review it as you would any script before running it, and note that it cannot be safely aggregated or auto-executed alongside YARA/Sigma/Suricata/CRS rules.

Rejected pattern present

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Format & documentation suggestions

Not a security issue — this rule is valid and was accepted as-is. These are optional fields/conventions its own format recommends, mainly affecting its quality score and how well it documents itself for other reviewers.

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[[ currentRule.title && currentRule.title.length > 60 ? currentRule.title.slice(0, 60) + '…' : currentRule.title ]]

[[ currentRule.title ]]

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