Detection rules › Kusto

CYFIRMA - Attack Surface - Weak Certificate Exposure - Medium Rule

This is a third-party alert feed, not a detection over modeled telemetry. The vendor product raised the finding; this rule forwards it into the SIEM. It is searchable for reference but is excluded from the detection-rule browse and the ATT&CK coverage matrix.

Status: available
Severity: medium
Time window: 5m
Source: github.com/Azure/Azure-Sentinel

'This alert indicates that a weak or insecure SSL/TLS certificate has been detected on a public-facing asset monitored by Cyfirma. Such certificates do not meet modern encryption standards and are considered insecure, especially for handling sensitive transactions. This exposure increases the risk of man-in-the-middle attacks and loss of data integrity or confidentiality. Immediate remediation is advised by replacing weak certificates with strong, industry-compliant ones.'

MITRE ATT&CK coverage

Tactic	Techniques
Reconnaissance	`T1595` Active Scanning
Resource Development	`T1588` Obtain Capabilities
Initial Access	`T1190` Exploit Public-Facing Application
Defense Impairment	`T1553` Subvert Trust Controls
Credential Access	`T1552` Unsecured Credentials

Rule body kusto

id: 5a617ff2-3e3d-44e7-b761-9f0d542ae191
name: CYFIRMA - Attack Surface - Weak Certificate Exposure - Medium Rule
description: |
  'This alert indicates that a weak or insecure SSL/TLS certificate has been detected on a public-facing asset monitored by Cyfirma. 
  Such certificates do not meet modern encryption standards and are considered insecure, especially for handling sensitive transactions. 
  This exposure increases the risk of man-in-the-middle attacks and loss of data integrity or confidentiality. 
  Immediate remediation is advised by replacing weak certificates with strong, industry-compliant ones.'
version: 1.0.1
kind: Scheduled
severity: Medium
requiredDataConnectors:
  - connectorId: CyfirmaAttackSurfaceAlertsConnector
    dataTypes:
      - CyfirmaASCertificatesAlerts_CL
queryFrequency: 5m
queryPeriod: 5m
triggerOperator: gt
triggerThreshold: 0
status: Available
tactics:
  - DefenseEvasion
  - ResourceDevelopment
  - Reconnaissance
  - InitialAccess
  - CredentialAccess
relevantTechniques:
  - T1553
  - T1588
  - T1595
  - T1190
  - T1552
query: |
  // Medium Severity Weak Certificate Exposure Detected
  let timeFrame = 5m;
  CyfirmaASCertificatesAlerts_CL
  | where severity == 'High' and TimeGenerated between (ago(timeFrame) .. now())
  | extend
      Description=description,
      FirstSeen=first_seen,
      LastSeen=last_seen,
      ValidFrom=valid_from,
      ValidTo=valid_to,
      RiskScore=risk_score,
      Domain=sub_domain,
      TopDomain=top_domain,
      Protocols=protocols,
      SelfSigned=self_signed,
      AlertUID=alert_uid,
      UID=uid,
      CertificateData= cert_data,
      CertificateHash=cert_hash,
      IssuedBy=issued_by,
      IssuedTo=issued_to,
      ProviderName='CYFIRMA',
      ProductName='DeCYFIR/DeTCT'
  | project
      TimeGenerated,
      Description,
      Domain,
      TopDomain,
      RiskScore,
      FirstSeen,
      LastSeen,
      ValidFrom,
      ValidTo,
      Protocols,
      SelfSigned,
      CertificateData,
      CertificateHash,
      IssuedBy,
      IssuedTo,
      ProviderName,
      ProductName
entityMappings:
  - entityType: DNS
    fieldMappings:
      - identifier: DomainName
        columnName: HostName
  - entityType: Host
    fieldMappings:
      - identifier: HostName
        columnName: TopDomain
      - identifier: DnsDomain
        columnName: Domain
customDetails:
  TimeGenerated: TimeGenerated
  CertificateData: CertificateData
  CertificateHash: CertificateHash
  FirstSeen: FirstSeen
  LastSeen: LastSeen
  ValidFrom: ValidFrom
  ValidTo: ValidTo
  Protocols: Protocols
  SelfSigned: SelfSigned
  IssuedBy: IssuedBy
  IssuedTo: IssuedTo
  Description: Description
  RiskScore: RiskScore
  TopDomain: TopDomain
  Domain: Domain
alertDetailsOverride:
  alertDisplayNameFormat: CYFIRMA - Medium Severity Weak Certificate Exposure Detected for this Domain  - {{Domain}}
  alertDescriptionFormat: CYFIRMA - Medium Severity Weak Certificate Exposure Detected  - {{Description}}
  alertDynamicProperties:
    - alertProperty: ProductName
      value: ProductName
    - alertProperty: ProviderName
      value: ProviderName
incidentConfiguration:
  createIncident: true
  groupingConfiguration:
    enabled: false
    reopenClosedIncident: false
    lookbackDuration: PT5H
    matchingMethod: AllEntities
eventGroupingSettings:
  aggregationKind: AlertPerResult

Stages and Predicates

Parameters

let timeFrame = 5m;

Stage 1: `source`

CyfirmaASCertificatesAlerts_CL

Stage 2: `where`

| where severity == 'High' and TimeGenerated between (ago(timeFrame) .. now())

Stage 3: `extend`

| extend
    Description=description,
    FirstSeen=first_seen,
    LastSeen=last_seen,
    ValidFrom=valid_from,
    ValidTo=valid_to,
    RiskScore=risk_score,
    Domain=sub_domain,
    TopDomain=top_domain,
    Protocols=protocols,
    SelfSigned=self_signed,
    AlertUID=alert_uid,
    UID=uid,
    CertificateData= cert_data,
    CertificateHash=cert_hash,
    IssuedBy=issued_by,
    IssuedTo=issued_to,
    ProviderName='CYFIRMA',
    ProductName='DeCYFIR/DeTCT'

Stage 4: `project`

| project
    TimeGenerated,
    Description,
    Domain,
    TopDomain,
    RiskScore,
    FirstSeen,
    LastSeen,
    ValidFrom,
    ValidTo,
    Protocols,
    SelfSigned,
    CertificateData,
    CertificateHash,
    IssuedBy,
    IssuedTo,
    ProviderName,
    ProductName

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
`severity`	eq	`High` 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
`CertificateData`	`project`
`CertificateHash`	`project`
`Description`	`project`
`Domain`	`project`
`FirstSeen`	`project`
`IssuedBy`	`project`
`IssuedTo`	`project`
`LastSeen`	`project`
`ProductName`	`project`
`Protocols`	`project`
`ProviderName`	`project`
`RiskScore`	`project`
`SelfSigned`	`project`
`TimeGenerated`	`project`
`TopDomain`	`project`
`ValidFrom`	`project`
`ValidTo`	`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)

CYFIRMA - Attack Surface - Weak Certificate Exposure - Medium Rule

MITRE ATT&CK coverage

Rule body kusto

Stages and Predicates

Parameters

Stage 1: `source`

Stage 2: `where`

Stage 3: `extend`

Stage 4: `project`

Indicators

Output fields

Keyboard shortcuts

Search operators

CYFIRMA - Attack Surface - Weak Certificate Exposure - Medium Rule

MITRE ATT&CK coverage

Rule body kusto

Stages and Predicates

Parameters

Stage 1: source

Stage 2: where

Stage 3: extend

Stage 4: project

Indicators

Output fields

Stage 1: `source`

Stage 2: `where`

Stage 3: `extend`

Stage 4: `project`