Remote Desktop Network Brute force (ASIM Network Session schema)

Status: available
Severity: medium
Time window: 5m
Group by: DstPortNumber, EventResult, SrcIpAddr
Source: github.com/Azure/Azure-Sentinel

This detection identifies RDP application network traffic and filters any source/destination pair generating more than 25 events hard threshold.

MITRE ATT&CK coverage

Tactic	Techniques
Credential Access	`T1110` Brute Force

Event coverage

Provider	Event	Title
Sysmon	Event ID 3	Network connection
Security-Auditing	Event ID 5152	The Windows Filtering Platform blocked a packet.
Security-Auditing	Event ID 5154	The Windows Filtering Platform has permitted an application or service to listen on a port for incoming connections.
Security-Auditing	Event ID 5155	The Windows Filtering Platform has blocked an application or service from listening on a port for incoming connections.
Security-Auditing	Event ID 5156	The Windows Filtering Platform has permitted a connection.
Security-Auditing	Event ID 5157	The Windows Filtering Platform has blocked a connection.
Security-Auditing	Event ID 5158	The Windows Filtering Platform has permitted a bind to a local port.
Security-Auditing	Event ID 5159	The Windows Filtering Platform has blocked a bind to a local port.

Rule body kusto

id: b7dc801e-1e79-48bb-91e8-2229a8e6d40b
name: Remote Desktop Network Brute force (ASIM Network Session schema)
description: |
  'This detection identifies RDP application network traffic and filters any source/destination pair generating more than 25 events hard threshold.'
severity: Medium
status: Available 
tags:
  - Schema: ASimNetworkSessions
    SchemaVersion: 0.2.4
requiredDataConnectors: []
queryFrequency: 1h
queryPeriod: 1h
triggerOperator: gt
triggerThreshold: 0
tactics:
  - CredentialAccess
relevantTechniques:
  - T1110
query: |
  // Start of the query and  Filter events that resulted in failure
  _Im_NetworkSession(eventresult="Failure")
  // Filter out private source IP addresses and focus on specific destination port (3389)
  // Also, ensure that the source and destination IP addresses are not the same
  | where not(ipv4_is_private(SrcIpAddr)) and tostring(DstPortNumber) has_any ("3389") and SrcIpAddr != DstIpAddr
  // Summarize the data by source and destination IP addresses, destination port number, network protocol, and event result
  // Also, bin the time generated in 5-minute intervals
  // Calculate the minimum and maximum time generated, the sum of event counts, and a set of up to 10 event vendors
  | summarize Starttime= min(TimeGenerated),EndTime= max(TimeGenerated),TargettedIPs=dcount(DstIpAddr),Eventscount=sum(EventCount),EventVendors=make_set(EventVendor,10) by SrcIpAddr,DstPortNumber,EventResult, bin(TimeGenerated, 5m)
  // Filter the summarized data to include only those with an event count of 25 or more
  | where Eventscount >= 25
entityMappings:
  - entityType: IP
    fieldMappings:
      - identifier: Address
        columnName: SrcIpAddr
eventGroupingSettings:
  aggregationKind: AlertPerResult
version: 1.0.0
kind: Scheduled

Stages and Predicates

Stage 1: `source`

_Im_NetworkSession(eventresult="Failure")

Stage 2: `where`

| where not(ipv4_is_private(SrcIpAddr)) and tostring(DstPortNumber) has_any ("3389") and SrcIpAddr != DstIpAddr

Stage 3: `summarize`

| summarize Starttime= min(TimeGenerated),EndTime= max(TimeGenerated),TargettedIPs=dcount(DstIpAddr),Eventscount=sum(EventCount),EventVendors=make_set(EventVendor,10) by SrcIpAddr,DstPortNumber,EventResult, bin(TimeGenerated, 5m)

Threshold: ge 25

Stage 4: `where`

| where Eventscount >= 25

Exclusions

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

Field	Kind	Excluded values
`SrcIpAddr`	cidr_match	`10.0.0.0/8`, `172.16.0.0/12`, `192.168.0.0/16`, `169.254.0.0/16`, `127.0.0.0/8`

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
`DstPortNumber`	match	`3389` transforms: `tostring`
`Eventscount`	ge	`25` transforms: `cased`
`SrcIpAddr`	ne	`DstIpAddr` transforms: `cased` corpus 2 (kusto 2)

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
`DstPortNumber`	`summarize`
`EndTime`	`summarize`
`EventResult`	`summarize`
`EventVendors`	`summarize`
`Eventscount`	`summarize`
`SrcIpAddr`	`summarize`
`Starttime`	`summarize`
`TargettedIPs`	`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
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`Enter`	Open highlighted result
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`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)

Remote Desktop Network Brute force (ASIM Network Session schema)

MITRE ATT&CK coverage

Event coverage

Rule body kusto

Stages and Predicates

Stage 1: `source`

Stage 2: `where`

Stage 3: `summarize`

Stage 4: `where`

Exclusions

Indicators

Output fields

Keyboard shortcuts

Search operators

Remote Desktop Network Brute force (ASIM Network Session schema)

MITRE ATT&CK coverage

Event coverage

Rule body kusto

Stages and Predicates

Stage 1: source

Stage 2: where

Stage 3: summarize

Stage 4: where

Exclusions

Indicators

Output fields

Stage 1: `source`

Stage 2: `where`

Stage 3: `summarize`

Stage 4: `where`