Nanocore 20230904 Dropped File

KQL detection rule by reversinglabs · MIT

this query identifies potential malicious files dropped by recent nanocore samples

// this query identifies potential malicious files dropped by recent nanocore samples
let DroppedFile = @"C:\Program Files (x86)\DHCP Monitor\dhcpmon.exe";
let DroppedFileLog = @"(?i)C:\\Users\\.*\\AppData\\Local\\Microsoft\\CLR_V4.0_32\\UsageLogs\\dhcpmon.exe.log";
(union isfuzzy=true
(DeviceFileEvents
| where ActionType == "FileCreated"
| where FolderPath == DroppedFile or FolderPath matches regex DroppedFileLog
| extend timestamp = TimeGenerated, HostCustomEntity = DeviceName),
(SysmonParser
| where EventID == 11
| where TargetFilename == DroppedFile or TargetFilename matches regex DroppedFileLog))

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

ee55514e-5f8a-4bbc-9db1-faa4cdc822ac

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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

[[ reason ]]

What does this mean?

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.

[[ reason ]]

What do these messages mean?

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

[[ currentRule.title ]]

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