SSH - Potential Brute Force

Severity: low
Time window: 4h
Group by: Computer, IPAddress, _ResourceId, ip, user
Source: github.com/Azure/Azure-Sentinel

'Identifies an IP address that had 15 failed attempts to sign in via SSH in a 4 hour block during a 24 hour time period. Please note that entity mapping for arrays is not supported, so when there is a single value in an array, we will pull that value from the array as a single string to populate the entity to support entity mapping features within Sentinel. Additionally, if the array is multivalued, we will input a string to indicate this with a unique hash so that matching will not occur. As an example - ComputerList is an array that we check for a single value and write that into the HostName field for use in the entity mapping within Sentinel.'

MITRE ATT&CK coverage

Tactic	Techniques
Credential Access	`T1110` Brute Force

Rule body kusto

id: e1ce0eab-10d1-4aae-863f-9a383345ba88
name: SSH - Potential Brute Force
description: |
  'Identifies an IP address that had 15 failed attempts to sign in via SSH in a 4 hour block during a 24 hour time period.
   Please note that entity mapping for arrays is not supported, so when there is a single value in an array, we will pull that value from the array as a single string to populate the entity to support entity mapping features within Sentinel. Additionally, if the array is multivalued, we will input a string to indicate this with a unique hash so that matching will not occur.
   As an example - ComputerList is an array that we check for a single value and write that into the HostName field for use in the entity mapping within Sentinel.'
severity: Low
requiredDataConnectors:
  - connectorId: Syslog
    dataTypes:
      - Syslog
  - connectorId: SyslogAma
    dataTypes:
      - Syslog
queryFrequency: 1d
queryPeriod: 1d
triggerOperator: gt
triggerThreshold: 0
tactics:
  - CredentialAccess
relevantTechniques:
  - T1110
query: |
  let threshold = 15;
  Syslog
  | where ProcessName =~ "sshd"
  | where SyslogMessage contains "Failed password for invalid user"
  | parse kind=relaxed SyslogMessage with * "invalid user " user " from " ip " port" port " ssh2" *
  // using distinct below as it has been seen that Syslog can duplicate entries depending on implementation
  | distinct TimeGenerated, Computer, user, ip, port, SyslogMessage, _ResourceId
  | summarize EventTimes = make_list(TimeGenerated), PerHourCount = count() by bin(TimeGenerated,4h), ip, Computer, user, _ResourceId
  | where PerHourCount > threshold
  | mvexpand EventTimes
  | extend EventTimes = tostring(EventTimes)
  | summarize StartTime = min(EventTimes), EndTime = max(EventTimes), UserList = make_set(user), ComputerList = make_set(Computer), ResourceIdList = make_set(_ResourceId), sum(PerHourCount) by IPAddress = ip
  // bringing through single computer and user if array only has 1, otherwise, referencing the column and hashing the ComputerList or UserList so we don't get accidental entity matches when reviewing alerts
  | extend HostName = iff(array_length(ComputerList) == 1, tostring(ComputerList[0]), strcat("SeeComputerListField","_", tostring(hash(tostring(ComputerList)))))
  | extend Account = iff(array_length(ComputerList) == 1, tostring(UserList[0]), strcat("SeeUserListField","_", tostring(hash(tostring(UserList)))))
  | extend ResourceId = iff(array_length(ResourceIdList) == 1, tostring(ResourceIdList[0]), strcat("SeeResourceIdListField","_", tostring(hash(tostring(ResourceIdList)))))
entityMappings:
  - entityType: Account
    fieldMappings:
      - identifier: Name
        columnName: Account
  - entityType: IP
    fieldMappings:
      - identifier: Address
        columnName: IPAddress
  - entityType: Host
    fieldMappings:
      - identifier: HostName
        columnName: HostName
  - entityType: AzureResource
    fieldMappings:
      - identifier: ResourceId
        columnName: ResourceId
version: 1.1.5
kind: Scheduled

Stages and Predicates

Parameters

let threshold = 15;

Stage 1: `source`

Syslog

Stage 2: `where`

| where ProcessName =~ "sshd"

Stage 3: `where`

| where SyslogMessage contains "Failed password for invalid user"

Stage 4: `parse`

| parse kind=relaxed SyslogMessage with * "invalid user " user " from " ip " port" port " ssh2" *

Stage 5: `distinct`

| distinct TimeGenerated, Computer, user, ip, port, SyslogMessage, _ResourceId

Stage 6: `summarize`

| summarize EventTimes = make_list(TimeGenerated), PerHourCount = count() by bin(TimeGenerated,4h), ip, Computer, user, _ResourceId

Threshold: gt 15

Stage 7: `where`

| where PerHourCount > threshold

Stage 8: `mv-expand`

| mvexpand EventTimes

Stage 9: `extend`

| extend EventTimes = tostring(EventTimes)

Stage 10: `summarize`

| summarize StartTime = min(EventTimes), EndTime = max(EventTimes), UserList = make_set(user), ComputerList = make_set(Computer), ResourceIdList = make_set(_ResourceId), sum(PerHourCount) by IPAddress = ip

Stage 11: `extend` (3 consecutive steps)

| extend HostName = iff(array_length(ComputerList) == 1, tostring(ComputerList[0]), strcat("SeeComputerListField","_", tostring(hash(tostring(ComputerList)))))
| extend Account = iff(array_length(ComputerList) == 1, tostring(UserList[0]), strcat("SeeUserListField","_", tostring(hash(tostring(UserList)))))
| extend ResourceId = iff(array_length(ResourceIdList) == 1, tostring(ResourceIdList[0]), strcat("SeeResourceIdListField","_", tostring(hash(tostring(ResourceIdList)))))

HostName =

ifComputerList == 1tostring(ComputerList[0])

elsestrcat("SeeComputerListField", "_", tostring(hash(tostring(ComputerList))))

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
`PerHourCount`	gt	`15` transforms: `cased`
`ProcessName`	eq	`sshd`
`SyslogMessage`	contains	`Failed password for invalid user`

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
`ComputerList`	`summarize`
`EndTime`	`summarize`
`IPAddress`	`summarize`
`ResourceIdList`	`summarize`
`StartTime`	`summarize`
`UserList`	`summarize`
`HostName`	`extend`
`Account`	`extend`
`ResourceId`	`extend`

`j` / `k`	Scroll down / up
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`f`	Follow link (`Shift` = new tab)
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`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)

SSH - Potential Brute Force

MITRE ATT&CK coverage

Rule body kusto

Stages and Predicates

Parameters

Stage 1: `source`

Stage 2: `where`

Stage 3: `where`

Stage 4: `parse`

Stage 5: `distinct`

Stage 6: `summarize`

Stage 7: `where`

Stage 8: `mv-expand`

Stage 9: `extend`

Stage 10: `summarize`

Stage 11: `extend` (3 consecutive steps)

Indicators

Output fields

Keyboard shortcuts

Search operators

SSH - Potential Brute Force

MITRE ATT&CK coverage

Rule body kusto

Stages and Predicates

Parameters

Stage 1: source

Stage 2: where

Stage 3: where

Stage 4: parse

Stage 5: distinct

Stage 6: summarize

Stage 7: where

Stage 8: mv-expand

Stage 9: extend

Stage 10: summarize

Stage 11: extend (3 consecutive steps)

Indicators

Output fields

Stage 1: `source`

Stage 2: `where`

Stage 3: `where`

Stage 4: `parse`

Stage 5: `distinct`

Stage 6: `summarize`

Stage 7: `where`

Stage 8: `mv-expand`

Stage 9: `extend`

Stage 10: `summarize`

Stage 11: `extend` (3 consecutive steps)