Hunt Device Discovery Subnet Ranges

Group by: IPv4Dhcp, NetworkName
Author: Robbe Van den Daele
Source: github.com/HybridBrothers/Hunting-Queries-Detection-Rules

This KQL query helps you identify which subnet ranges are behind the Microsoft Defender for Endpoint Device Discovery 'Monitored Networks' page. By using this query you can investigate if all of your corporate networks are being monitored and change monitored states effectivly. More information can be found in the references.

References

https://hybridbrothers.com/mde-device-discovery-improving-the-monitored-network-page/

Rule body yaml

// OPTIONAL - Device cap used to ignore network with less then X devices in them
let device_cap = 0;
DeviceNetworkInfo
| where Timestamp > ago(7d)
// Ignore empty networks
| where ConnectedNetworks  != ""
// Get networks data
| extend ConnectedNetworksExp = parse_json(ConnectedNetworks)
| mv-expand bagexpansion = array ConnectedNetworks=ConnectedNetworksExp
| extend NetworkName = tostring(ConnectedNetworks ["Name"]), NetworkDescription = tostring(ConnectedNetworks ["Description"]), NetworkCategory = tostring(ConnectedNetworks ["Category"])
// Get subnet data for IPv4 Addresses
| extend IPAddressesExp = parse_json(IPAddresses)
| mv-expand bagexpansion = array IPAddresses=IPAddressesExp
| extend IPAddress = tostring(IPAddresses ["IPAddress"]), SubnetPrefix = tolong(IPAddresses ["SubnetPrefix"])
| extend NetworkAddress = format_ipv4(IPAddress, SubnetPrefix)
| extend SubnetRange = strcat(NetworkAddress, "/", SubnetPrefix)
// Exclude IPv6 and APIPPA
| where SubnetPrefix <= 32
| where IPAddress !startswith "169.254"
// Ignore unidentified networks
| where not(NetworkName has_any ("Unidentified", "Identifying..."))
// Provide list
| distinct DeviceId, NetworkName, IPv4Dhcp, SubnetRange
| summarize Devices = count(), SubnetRanges = make_set(SubnetRange) by NetworkName, IPv4Dhcp
// Ignore network with very low device count
| where Devices >= device_cap
| sort by Devices desc

// OPTIONAL - Device cap used to ignore network with less then X devices in them
let device_cap = 0;
DeviceNetworkInfo
| where TimeGenerated > ago(7d)
// Ignore empty networks
| where ConnectedNetworks  != ""
// Get networks data
| extend ConnectedNetworksExp = parse_json(ConnectedNetworks)
| mv-expand bagexpansion = array ConnectedNetworks=ConnectedNetworksExp
| extend NetworkName = tostring(ConnectedNetworks ["Name"]), NetworkDescription = tostring(ConnectedNetworks ["Description"]), NetworkCategory = tostring(ConnectedNetworks ["Category"])
// Get subnet data for IPv4 Addresses
| extend IPAddressesExp = parse_json(IPAddresses)
| mv-expand bagexpansion = array IPAddresses=IPAddressesExp
| extend IPAddress = tostring(IPAddresses ["IPAddress"]), SubnetPrefix = tolong(IPAddresses ["SubnetPrefix"])
| extend NetworkAddress = format_ipv4(IPAddress, SubnetPrefix)
| extend SubnetRange = strcat(NetworkAddress, "/", SubnetPrefix)
// Exclude IPv6 and APIPPA
| where SubnetPrefix <= 32
| where IPAddress !startswith "169.254"
// Ignore unidentified networks
| where not(NetworkName has_any ("Unidentified", "Identifying..."))
// Provide list
| distinct DeviceId, NetworkName, IPv4Dhcp, SubnetRange
| summarize Devices = count(), SubnetRanges = make_set(SubnetRange) by NetworkName, IPv4Dhcp
// Ignore network with very low device count
| where Devices >= device_cap
| sort by Devices desc

Stages and Predicates

Parameters

let device_cap = 0;

Stage 1: `source`

DeviceNetworkInfo

Stage 2: `where`

| where Timestamp > ago(7d)

Stage 3: `where`

| where ConnectedNetworks  != ""

Stage 4: `extend`

| extend ConnectedNetworksExp = parse_json(ConnectedNetworks)

Stage 5: `mv-expand`

| mv-expand bagexpansion = array ConnectedNetworks=ConnectedNetworksExp

Stage 6: `extend`

| extend NetworkName = tostring(ConnectedNetworks ["Name"]), NetworkDescription = tostring(ConnectedNetworks ["Description"]), NetworkCategory = tostring(ConnectedNetworks ["Category"])

Stage 7: `extend`

| extend IPAddressesExp = parse_json(IPAddresses)

Stage 8: `mv-expand`

| mv-expand bagexpansion = array IPAddresses=IPAddressesExp

Stage 9: `extend` (3 consecutive steps)

| extend IPAddress = tostring(IPAddresses ["IPAddress"]), SubnetPrefix = tolong(IPAddresses ["SubnetPrefix"])
| extend NetworkAddress = format_ipv4(IPAddress, SubnetPrefix)
| extend SubnetRange = strcat(NetworkAddress, "/", SubnetPrefix)

Stage 10: `where`

| where SubnetPrefix <= 32

Stage 11: `where`

| where IPAddress !startswith "169.254"

Stage 12: `where`

| where not(NetworkName has_any ("Unidentified", "Identifying..."))

Stage 13: `distinct`

| distinct DeviceId, NetworkName, IPv4Dhcp, SubnetRange

Stage 14: `summarize`

| summarize Devices = count(), SubnetRanges = make_set(SubnetRange) by NetworkName, IPv4Dhcp

Threshold: ge 0

Stage 15: `where`

| where Devices >= device_cap

Stage 16: `sort`

| sort by Devices desc

Exclusions

Top-level NOT(...) conjuncts: predicates this rule actively suppresses.

Field	Kind	Excluded values
`IPAddress`	starts_with	`169.254`
`NetworkName`	match	`Unidentified`, `Identifying...`

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
`Devices`	ge	`0` transforms: `cased`
`SubnetPrefix`	le	`32` transforms: `cased`

Output fields

Fields the rule emits when it matches. Chronicle authors list these in the outcome block; they appear on the detection and $risk_score drives alerting. Sentinel / Defender XDR rules build them up through project / summarize / extend stages. Sentinel maps these into alert fields via entityMappings and customDetails; Defender XDR custom detections surface them as alert fields directly.

Field	Source
`Devices`	`summarize`
`IPv4Dhcp`	`summarize`
`NetworkName`	`summarize`
`SubnetRanges`	`summarize`

`j` / `k`	Scroll down / up
`d` / `u`	Half-page down / up
`gg` / `G`	Top / bottom
`h` / `l`	History back / forward
`f`	Follow link (`Shift` = new tab)
`/`	Focus search
`?`	Toggle this help
`↑` / `↓`	Navigate search results
`Enter`	Open highlighted result
`Esc`	Close results / dialog

`type:`	`events` / `rules` / `providers`
`vendor:`	`sigma` / `elastic` / `splunk` / `kusto` / `chronicle` (vendor name alone also works: `sigma:`, `kql:`, `secops:`…)
`tactic:`	TA-id, slug, or name: `credential_access`, `TA0006`
`technique:`	technique or sub-technique ID: `T1003`, `T1003.001` (alias `tech:`)
`severity:`	`critical` / `high` / `medium` / `low` / `informational` (alias `sev:`)
`risk_score`	Numeric comparison on the Elastic risk score (0 to 100): `risk_score>50`, `risk_score<=20`, `risk_score=99` (alias `risk`; Elastic rules only)
`stages:`	Rules with exactly N pipeline stages
`correlation:`	`single_event` / `sequence` / `alternatives` / `alternatives_cross_log` / `all_required` / `correlated`
`with:`	Co-occurrence event-id; stacks (`with:4624 with:4769`) to require all, while a comma list in one occurrence (`with:4624,4769`) is an either-or group. Implies multi-event
`like:`	Structural neighbors of a rule slug (equivalents + subsumption stricter / broader): `like:comsvcs_lsass_memory_dump-splunk-sysmon`
`groupby:`	Entity-grouping substring match against `group_by_keys`: `groupby:user`, `groupby:host`
`uses:`	Rules whose predicate tree touches the field (any kind, any value): `uses:CommandLine`
`excludes:`	Rules with top-level `not()` clauses on the field (FP whitelists): `excludes:ParentImage`
`field:` / `value:`	Predicate search; narrows rule cards to those with a matching leaf and drives the indicator tier. Unquoted = substring, wildcards allowed (`value:mimikatz`)
`indicator:`	Shorthand for `field:F value:V`: `indicator:Image=*\powershell.exe`
`kind:`	Filter by predicate kind. Narrows rule cards to those carrying a matching predicate leaf (`vendor:elastic kind:cidr_match`) and drives the indicator tier: `contains` / `starts_with` / `ends_with` / `regex` / `cidr` / `eq` / `in` … (operator aliases `op:`/`match:`)
`has:` / `no:`	`sample`, `field`, `notes`, `refs`, `trace`, `thirdparty`, `rule`, `pattern`, `timewindow`, `threshold`, `newterms`, `sigma`/`elastic`/`splunk`/`kusto`/`chronicle`
`-op:val`	Exclude matches; works on most operators but not `type:`/`like:`/`has:`/`no:` (use `no:<flag>` to exclude a rule flag): `tactic:execution -vendor:splunk`. Standalone `-kind:`/`-field:`/`-value:` drop every rule carrying a matching predicate leaf (`type:rules -kind:is_null`)
`field:"…"` / `value:"…"`	Quoted value = anchored exact match (also allows spaces): `value:"net user"`
`a,b`	Comma = OR inside one operator (`vendor:sigma,elastic`, `severity:high,critical`); repeating a facet merges the same way. `field:`/`value:` never split (literal commas)
`vendors:` / `stage:`	Singular and plural spellings fold to the canonical operator and value: `tactics:` = `tactic:`, `type:event` = `type:events`, `correlation:sequences` = `correlation:sequence`, `has:thresholds` = `has:threshold`
`"quoted phrase"`	Exact-match a multi-word phrase (free text)

Hunt Device Discovery Subnet Ranges

References

Rule body yaml

Stages and Predicates

Parameters

Stage 1: `source`

Stage 2: `where`

Stage 3: `where`

Stage 4: `extend`

Stage 5: `mv-expand`

Stage 6: `extend`

Stage 7: `extend`

Stage 8: `mv-expand`

Stage 9: `extend` (3 consecutive steps)

Stage 10: `where`

Stage 11: `where`

Stage 12: `where`

Stage 13: `distinct`

Stage 14: `summarize`

Stage 15: `where`

Stage 16: `sort`

Exclusions

Indicators

Output fields

Keyboard shortcuts

Search operators

Hunt Device Discovery Subnet Ranges

References

Rule body yaml

Stages and Predicates

Parameters

Stage 1: source

Stage 2: where

Stage 3: where

Stage 4: extend

Stage 5: mv-expand

Stage 6: extend

Stage 7: extend

Stage 8: mv-expand

Stage 9: extend (3 consecutive steps)

Stage 10: where

Stage 11: where

Stage 12: where

Stage 13: distinct

Stage 14: summarize

Stage 15: where

Stage 16: sort

Exclusions

Indicators

Output fields

Stage 1: `source`

Stage 2: `where`

Stage 3: `where`

Stage 4: `extend`

Stage 5: `mv-expand`

Stage 6: `extend`

Stage 7: `extend`

Stage 8: `mv-expand`

Stage 9: `extend` (3 consecutive steps)

Stage 10: `where`

Stage 11: `where`

Stage 12: `where`

Stage 13: `distinct`

Stage 14: `summarize`

Stage 15: `where`

Stage 16: `sort`