Detect URLs containing known malicious keywords or commands (ASIM Web Session)

Status: available
Severity: high
Time window: 5m
Group by: Decoded_url, DstIpAddr, SrcHostname, SrcIpAddr, SrcUsername, Url
Source: github.com/Azure/Azure-Sentinel

'The utilization of system commands or functions in the request URL may suggest that an attacker is trying to gain unauthorized access to the environment by exploiting a vulnerable service.'

MITRE ATT&CK coverage

Tactic	Techniques
Initial Access	`T1133` External Remote Services, `T1190` Exploit Public-Facing Application
Command & Control	`T1071` Application Layer Protocol

Rule body kusto

id: 32c08696-2e37-4730-86f8-97d9c8b184c9
name: Detect URLs containing known malicious keywords or commands (ASIM Web Session)
description: |
  'The utilization of system commands or functions in the request URL may suggest that an attacker is trying to gain unauthorized access to the environment by exploiting a vulnerable service.'
severity: High
status: Available 
tags:
  - Schema: WebSession
    SchemaVersion: 0.2.6
requiredDataConnectors: []
queryFrequency: 5m
queryPeriod: 5m
triggerOperator: gt
triggerThreshold: 0
tactics:
  - InitialAccess
  - CommandAndControl
relevantTechniques:
  - T1190
  - T1133
  - T1071
query: |
  let lookback = 5m;
  let RiskyCommandsInUrl = materialize(externaldata(Commands: string)
      [@"https://raw.githubusercontent.com/Azure/Azure-Sentinel/master/Sample%20Data/Feeds/CommandsInURL.csv"]
      with(format="csv", ignoreFirstRecord=True));
  let CustomRiskyCommandsInUrl = (_ASIM_GetWatchlistRaw("Web_RiskyCommandsInUrl") // Create new Watchlist and add your custom indicators(Optional)
      | extend
          Commands = tostring(WatchlistItem["Commands"])
      | project Commands
      | where isnotempty(Commands));
  let CombinedRiskyCommandsInUrl = union RiskyCommandsInUrl, CustomRiskyCommandsInUrl;
  let knownRiskyCommandsInUrl=toscalar(CombinedRiskyCommandsInUrl
      | where isnotempty(Commands)
      | summarize make_set(Commands, 1000));
  // You can add more keywords to the query as necessary, depending on the specific indicators you want to detect.
  _Im_WebSession (starttime=ago(lookback), eventresult='Success', url_has_any=knownRiskyCommandsInUrl)
  | where isnotempty(Url)
  | project Url, SrcIpAddr, SrcUsername, SrcHostname, DstIpAddr, TimeGenerated
  | extend Decoded_url = url_decode(Url)
  | where Decoded_url has_any (knownRiskyCommandsInUrl)
  | summarize
      EventCount=count(),
      EventStartTime=min(TimeGenerated),
      EventEndTime=max(TimeGenerated)
      by SrcIpAddr, SrcUsername, SrcHostname, Url, Decoded_url, DstIpAddr
  | extend
      Name = iif(SrcUsername contains "@", tostring(split(SrcUsername, '@', 0)[0]), SrcUsername),
      UPNSuffix = iif(SrcUsername contains "@", tostring(split(SrcUsername, '@', 1)[0]), "")
entityMappings:
  - entityType: IP
    fieldMappings:
      - identifier: Address
        columnName: SrcIpAddr
  - entityType: IP
    fieldMappings:
      - identifier: Address
        columnName: DstIpAddr
  - entityType: URL
    fieldMappings:
      - identifier: Url
        columnName: Url
  - entityType: Account
    fieldMappings:
      - identifier: FullName
        columnName: SrcUsername
      - identifier: Name
        columnName: Name
      - identifier: UPNSuffix
        columnName: UPNSuffix
eventGroupingSettings:
  aggregationKind: AlertPerResult
customDetails:
  EventCount: EventCount
  Decoded_url: Decoded_url
  EventStartTime: EventStartTime
  EventEndTime: EventEndTime
alertDetailsOverride:
  alertDisplayNameFormat: "User '{{SrcUsername}}' with IP '{{SrcIpAddr}}' has been identified as making request for URL '{{Url}}' that includes a recognizable malicious command"
version: 1.0.1
kind: Scheduled

Stages and Predicates

Parameters

let lookback = 5m;
let CombinedRiskyCommandsInUrl = union RiskyCommandsInUrl, CustomRiskyCommandsInUrl;

Let binding: `RiskyCommandsInUrl`

let RiskyCommandsInUrl = materialize(externaldata(Commands: string)
    [@"https://raw.githubusercontent.com/Azure/Azure-Sentinel/master/Sample%20Data/Feeds/CommandsInURL.csv"]
    with(format="csv", ignoreFirstRecord=True));

Let binding: `CustomRiskyCommandsInUrl`

let CustomRiskyCommandsInUrl = (_ASIM_GetWatchlistRaw("Web_RiskyCommandsInUrl")
    | extend
        Commands = tostring(WatchlistItem["Commands"])
    | project Commands
    | where isnotempty(Commands));

Let binding: `knownRiskyCommandsInUrl`

let knownRiskyCommandsInUrl = toscalar(CombinedRiskyCommandsInUrl
    | where isnotempty(Commands)
    | summarize make_set(Commands, 1000));

Derived from CombinedRiskyCommandsInUrl.

Stage 1: `source`

_Im_WebSession (starttime=ago(lookback), eventresult='Success', url_has_any=knownRiskyCommandsInUrl)

Stage 2: `where`

| where isnotempty(Url)

Stage 3: `project`

| project Url, SrcIpAddr, SrcUsername, SrcHostname, DstIpAddr, TimeGenerated

Stage 4: `extend`

| extend Decoded_url = url_decode(Url)

Stage 5: `where`

| where Decoded_url has_any (knownRiskyCommandsInUrl)

References knownRiskyCommandsInUrl (defined above).

Stage 6: `summarize`

| summarize
    EventCount=count(),
    EventStartTime=min(TimeGenerated),
    EventEndTime=max(TimeGenerated)
    by SrcIpAddr, SrcUsername, SrcHostname, Url, Decoded_url, DstIpAddr

Stage 7: `extend`

| extend
    Name = iif(SrcUsername contains "@", tostring(split(SrcUsername, '@', 0)[0]), SrcUsername),
    UPNSuffix = iif(SrcUsername contains "@", tostring(split(SrcUsername, '@', 1)[0]), "")

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
`Decoded_url`	match	`knownRiskyCommandsInUrl`
`Url`	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
`Decoded_url`	`summarize`
`DstIpAddr`	`summarize`
`EventCount`	`summarize`
`EventEndTime`	`summarize`
`EventStartTime`	`summarize`
`SrcHostname`	`summarize`
`SrcIpAddr`	`summarize`
`SrcUsername`	`summarize`
`Url`	`summarize`
`Name`	`extend`
`UPNSuffix`	`extend`

`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)

Detect URLs containing known malicious keywords or commands (ASIM Web Session)

MITRE ATT&CK coverage

Rule body kusto

Stages and Predicates

Parameters

Let binding: `RiskyCommandsInUrl`

Let binding: `CustomRiskyCommandsInUrl`

Let binding: `knownRiskyCommandsInUrl`

Stage 1: `source`

Stage 2: `where`

Stage 3: `project`

Stage 4: `extend`

Stage 5: `where`

Stage 6: `summarize`

Stage 7: `extend`

Indicators

Output fields

Keyboard shortcuts

Search operators

Detect URLs containing known malicious keywords or commands (ASIM Web Session)

MITRE ATT&CK coverage

Rule body kusto

Stages and Predicates

Parameters

Let binding: RiskyCommandsInUrl

Let binding: CustomRiskyCommandsInUrl

Let binding: knownRiskyCommandsInUrl

Stage 1: source

Stage 2: where

Stage 3: project

Stage 4: extend

Stage 5: where

Stage 6: summarize

Stage 7: extend

Indicators

Output fields

Let binding: `RiskyCommandsInUrl`

Let binding: `CustomRiskyCommandsInUrl`

Let binding: `knownRiskyCommandsInUrl`

Stage 1: `source`

Stage 2: `where`

Stage 3: `project`

Stage 4: `extend`

Stage 5: `where`

Stage 6: `summarize`

Stage 7: `extend`