Device Newhashaccessinglsass

KQL detection rule by reprise99 · MIT

Detect when a process with a hash not previously seen before in your environment accesses lsass.exe via an open process API call

//Detect when a process with a hash not previously seen before in your environment accesses lsass.exe via an open process API call

//Data connector required for this query - M365 Defender - Device* tables

//Microsoft Sentinel query
let knownhashes=
    DeviceEvents
    | where TimeGenerated > ago(30d) and TimeGenerated < ago (1d)
    | where ActionType == "OpenProcessApiCall"
    | where FileName == "lsass.exe"
    | distinct InitiatingProcessSHA256;
DeviceEvents
| where TimeGenerated > ago (1d)
| where ActionType == "OpenProcessApiCall"
| where FileName == "lsass.exe"
| where InitiatingProcessSHA256 !in (knownhashes)
| extend DesiredAccess = tostring(AdditionalFields.DesiredAccess)
| distinct
    DeviceName,
    InitiatingProcessAccountName,
    InitiatingProcessCommandLine,
    DesiredAccess

//Detect when a process with a hash not previously seen before in your environment accesses lsass.exe via an open process API call

//Data connector required for this query - Advanced Hunting license

//Advanced Hunting query
let knownhashes=
    DeviceEvents
    | where Timestamp > ago(30d) and Timestamp < ago (1d)
    | where ActionType == "OpenProcessApiCall"
    | where FileName == "lsass.exe"
    | distinct InitiatingProcessSHA256;
DeviceEvents
| where Timestamp > ago (1d)
| where ActionType == "OpenProcessApiCall"
| where FileName == "lsass.exe"
| where InitiatingProcessSHA256 !in (knownhashes)
| distinct DeviceName,
    InitiatingProcessAccountName,
    InitiatingProcessCommandLine,
    AdditionalFields

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

69a1edf0-e138-480c-a304-eb1f82b71b95

Propose edits, view related rules, and engage with the community through comments.

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 ]]

Community Discussion