Forescout-DNS_Sniff_Event_Monitor

Severity: medium
Time window: 5m
Group by: EmIpAddr, ipaddress
Source: github.com/Azure/Azure-Sentinel

This rule creates an incident when more than certain number of Dnsniff events are generated from a host

Rule body kusto

id: d272e277-f285-4dbc-ae2d-7f65ba64a79e
name: Forescout-DNS_Sniff_Event_Monitor
description: 'This rule creates an incident when more than certain number of Dnsniff events are generated from a host'
severity: Medium
requiredDataConnectors: []
queryFrequency: 5m
queryPeriod: 5m
triggerOperator: gt
triggerThreshold: 0
tactics: []
relevantTechniques: []
query:
  ForescoutHostProperties_CL
  | extend  d = parse_json(HostProperties)
  | where d.DnsniffEvent matches regex "DNS Query Type:.A;DNS Query/Response:.Query"
  | extend ipaddress = iif(isnotempty(Ipv4Addr), Ipv4Addr, (iif(isnotempty(Ipv6Addr), Ipv6Addr, "")))
  | where isnotempty(ipaddress) and isnotempty(EmIpAddr)
  | summarize NumEvents_d =count() by ipaddress, EmIpAddr
  | where NumEvents_d > 2
  | sort by NumEvents_d asc
  | project NumEvents_d, ipaddress, EmIpAddr

entityMappings:
  - entityType: IP
    fieldMappings:
      - identifier: Address
        columnName: ipaddress
customDetails:
  Ip: ipaddress
  NumEvents: NumEvents_d
  EmIp: EmIpAddr
alertDetailsOverride:
  alertDisplayNameFormat: Dnsniff-Address-Check
  alertDescriptionFormat: Dnsniff-Address-Check alert
version: 2.0.0
kind: Scheduled

Stages and Predicates

Stage 1: `source`

ForescoutHostProperties_CL

Stage 2: `extend`

| extend  d = parse_json(HostProperties)

Stage 3: `where`

| where d.DnsniffEvent matches regex "DNS Query Type:.A;DNS Query/Response:.Query"

Stage 4: `extend`

| extend ipaddress = iif(isnotempty(Ipv4Addr), Ipv4Addr, (iif(isnotempty(Ipv6Addr), Ipv6Addr, "")))

Stage 5: `where`

| where isnotempty(ipaddress) and isnotempty(EmIpAddr)

Stage 6: `summarize`

| summarize NumEvents_d =count() by ipaddress, EmIpAddr

Threshold: gt 2

Stage 7: `where`

| where NumEvents_d > 2

Stage 8: `sort`

| sort by NumEvents_d asc

Stage 9: `project`

| project NumEvents_d, ipaddress, EmIpAddr

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
`DnsniffEvent`	regex_match	`DNS Query Type:.A;DNS Query/Response:.Query`
`EmIpAddr`	is_not_null	(no value, null check)
`NumEvents_d`	gt	`2` transforms: `cased`
`ipaddress`	is_not_null	(no value, null check)

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
`EmIpAddr`	`project`
`NumEvents_d`	`project`
`ipaddress`	`project`

`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)

Forescout-DNS_Sniff_Event_Monitor

Rule body kusto

Stages and Predicates

Stage 1: `source`

Stage 2: `extend`

Stage 3: `where`

Stage 4: `extend`

Stage 5: `where`

Stage 6: `summarize`

Stage 7: `where`

Stage 8: `sort`

Stage 9: `project`

Indicators

Output fields

Keyboard shortcuts

Search operators

Forescout-DNS_Sniff_Event_Monitor

Rule body kusto

Stages and Predicates

Stage 1: source

Stage 2: extend

Stage 3: where

Stage 4: extend

Stage 5: where

Stage 6: summarize

Stage 7: where

Stage 8: sort

Stage 9: project

Indicators

Output fields

Stage 1: `source`

Stage 2: `extend`

Stage 3: `where`

Stage 4: `extend`

Stage 5: `where`

Stage 6: `summarize`

Stage 7: `where`

Stage 8: `sort`

Stage 9: `project`