AWS RDS Instance Modified to be Publicly Accessible

Severity: critical
Log types: AWS.CloudTrail
Tags: AWS, Persistence, Defense Evasion, Initial Access, Account Manipulation, Disable or Modify Cloud Firewall, External Remote Services, RDS
Reference: https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/USER_VPC.WorkingWithRDSInstanceinaVPC.html
Source: github.com/panther-labs/panther-analysis

Detects when an RDS instance or cluster is modified to become publicly accessible. This exposes the database to the internet and is used by attackers for persistence or data exfiltration. This detects the modification event in real-time, unlike static policy checks.

MITRE ATT&CK coverage

Tactic	Techniques
Initial Access	`T1133` External Remote Services
Persistence	`T1098` Account Manipulation, `T1133` External Remote Services
Stealth	`T1562.007` Impair Defenses: Disable or Modify Cloud Firewall

Rules detecting the same action

Other rules on this platform that filter on the same API call or operation.

AWS RDS DB Instance Made Public (Elastic)
AWS RDS DB Instance or Cluster Deletion Protection Disabled (Elastic)
AWS RDS DB Instance or Cluster Password Modified (Elastic)
AWS RDS Deletion Protection Disabled (Panther)
AWS RDS Master Password Change (Sigma)
AWS RDS Master Password Updated (Panther)
AWS RDS Snapshot Deleted (Elastic)
Modification or Deletion of an AWS RDS Cluster (Sigma)

Rule body yaml

AnalysisType: rule
Filename: aws_rds_instance_made_public.py
RuleID: "AWS.RDS.InstanceMadePublic"
DisplayName: "AWS RDS Instance Modified to be Publicly Accessible"
Enabled: true
LogTypes:
  - AWS.CloudTrail
Tags:
  - AWS
  - Persistence
  - Defense Evasion
  - Initial Access
  - Account Manipulation
  - Disable or Modify Cloud Firewall
  - External Remote Services
  - RDS
Severity: Critical
Description: >
  Detects when an RDS instance or cluster is modified to become publicly accessible. This exposes
  the database to the internet and is used by attackers for persistence or data exfiltration.
  This detects the modification event in real-time, unlike static policy checks.
Runbook: |
  1. Find all RDS modification events by the user ARN in the 24 hours before the alert
  2. Check if this database has been made public before by searching for ModifyDBInstance events with publiclyAccessible in the past 90 days
  3. Look for database connection attempts from external IPs in the 6 hours after this modification
  3. Find all API calls from the sourceIPAddress in the 6 hours before and after the alert to identify other suspicious modifications
  4. Immediately revert publiclyAccessible to false if unauthorized, then review VPC security groups for overly permissive rules (0.0.0.0/0)
  5. Check RDS database logs for any access attempts from external IPs in the time window after this modification
Reference: https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/USER_VPC.WorkingWithRDSInstanceinaVPC.html
Reports:
  MITRE ATT&CK:
    - TA0003:T1098  # Account Manipulation
    - TA0005:T1562.007  # Disable or Modify Cloud Firewall
    - TA0001:T1133  # External Remote Services
DedupPeriodMinutes: 60
SummaryAttributes:
  - eventName
  - userIdentity:principalId
  - requestParameters:dBInstanceIdentifier
  - requestParameters:dBClusterIdentifier
  - requestParameters:publiclyAccessible
  - p_any_aws_account_ids
Threshold: 1
Tests:
  - Name: RDS Instance Made Public
    ExpectedResult: true
    Log:
      eventVersion: "1.08"
      userIdentity:
        type: AssumedRole
        principalId: "AIDAI23HXS3EXAMPLE:developer"
        arn: "arn:aws:sts::123456789012:assumed-role/DeveloperRole/developer"
        accountId: "123456789012"
        accessKeyId: "ASIAIOSFODNN7EXAMPLE"
        sessionContext:
          sessionIssuer:
            type: Role
            principalId: "AIDAI23HXS3EXAMPLE"
            arn: "arn:aws:iam::123456789012:role/DeveloperRole"
            accountId: "123456789012"
            userName: DeveloperRole
      eventTime: "2024-01-15T16:45:00Z"
      eventSource: rds.amazonaws.com
      eventName: ModifyDBInstance
      awsRegion: us-east-1
      sourceIPAddress: "203.0.113.45"
      userAgent: "aws-cli/2.13.0"
      requestParameters:
        dBInstanceIdentifier: "production-db"
        publiclyAccessible: true
        applyImmediately: true
      responseElements:
        dBInstanceIdentifier: "production-db"
        dBInstanceStatus: "modifying"
        publiclyAccessible: true
        pendingModifiedValues:
          publiclyAccessible: true
      requestID: "a1b2c3d4-e5f6-7890-abcd-ef1234567890"
      eventID: "f1e2d3c4-b5a6-7890-1234-567890abcdef"
      readOnly: false
      eventType: AwsApiCall
      managementEvent: true
      recipientAccountId: "123456789012"
      eventCategory: Management

  - Name: RDS Cluster Made Public with Security Group Changes
    ExpectedResult: true
    Log:
      eventVersion: "1.08"
      userIdentity:
        type: IAMUser
        principalId: "AIDAI23HXS3EXAMPLE"
        arn: "arn:aws:iam::123456789012:user/contractor"
        accountId: "123456789012"
        accessKeyId: "AKIAIOSFODNN7EXAMPLE"
        userName: contractor
      eventTime: "2024-01-15T16:45:00Z"
      eventSource: rds.amazonaws.com
      eventName: ModifyDBCluster
      awsRegion: us-west-2
      sourceIPAddress: "198.51.100.10"
      userAgent: "Boto3/1.26.0"
      requestParameters:
        dBClusterIdentifier: "aurora-cluster"
        publiclyAccessible: true
        vPCSecurityGroupIds:
          - "sg-0123456789abcdef0"
        applyImmediately: true
      responseElements:
        dBClusterIdentifier: "aurora-cluster"
        status: "modifying"
        publiclyAccessible: true
      requestID: "b2c3d4e5-f6a7-8901-bcde-f1234567890a"
      eventID: "g2f3e4d5-c6b7-8901-2345-678901bcdefg"
      readOnly: false
      eventType: AwsApiCall
      managementEvent: true
      recipientAccountId: "123456789012"
      eventCategory: Management

  - Name: RDS Instance Made Private - No Alert
    ExpectedResult: false
    Log:
      eventVersion: "1.08"
      userIdentity:
        type: AssumedRole
        principalId: "AIDAI23HXS3EXAMPLE:admin"
        arn: "arn:aws:sts::123456789012:assumed-role/AdminRole/admin"
        accountId: "123456789012"
        accessKeyId: "ASIAIOSFODNN7EXAMPLE"
      eventTime: "2024-01-15T16:45:00Z"
      eventSource: rds.amazonaws.com
      eventName: ModifyDBInstance
      awsRegion: us-east-1
      sourceIPAddress: "10.0.1.100"
      userAgent: "console.amazonaws.com"
      requestParameters:
        dBInstanceIdentifier: "production-db"
        publiclyAccessible: false
        applyImmediately: true
      responseElements:
        dBInstanceIdentifier: "production-db"
        dBInstanceStatus: "modifying"
        publiclyAccessible: false
      requestID: "c3d4e5f6-a7b8-9012-cdef-1234567890ab"
      eventID: "h3g4f5e6-d7c8-9012-3456-789012cdefgh"
      readOnly: false
      eventType: AwsApiCall
      managementEvent: true
      recipientAccountId: "123456789012"
      eventCategory: Management

  - Name: RDS Modification Without Public Access Change
    ExpectedResult: false
    Log:
      eventVersion: "1.08"
      userIdentity:
        type: AssumedRole
        principalId: "AIDAI23HXS3EXAMPLE:user"
        arn: "arn:aws:sts::123456789012:assumed-role/DBARole/user"
        accountId: "123456789012"
        accessKeyId: "ASIAIOSFODNN7EXAMPLE"
      eventTime: "2024-01-15T16:45:00Z"
      eventSource: rds.amazonaws.com
      eventName: ModifyDBInstance
      awsRegion: us-east-1
      sourceIPAddress: "10.0.1.50"
      userAgent: "aws-cli/2.13.0"
      requestParameters:
        dBInstanceIdentifier: "production-db"
        allocatedStorage: 200
        applyImmediately: false
      responseElements:
        dBInstanceIdentifier: "production-db"
        dBInstanceStatus: "modifying"
        allocatedStorage: 200
      requestID: "d4e5f6a7-b8c9-0123-def0-1234567890bc"
      eventID: "i4h5g6f7-e8d9-0123-4567-890123defghi"
      readOnly: false
      eventType: AwsApiCall
      managementEvent: true
      recipientAccountId: "123456789012"
      eventCategory: Management

  - Name: RDS Modification Failed
    ExpectedResult: false
    Log:
      eventVersion: "1.08"
      userIdentity:
        type: IAMUser
        principalId: "AIDAI23HXS3EXAMPLE"
        arn: "arn:aws:iam::123456789012:user/developer"
        accountId: "123456789012"
        accessKeyId: "AKIAIOSFODNN7EXAMPLE"
        userName: developer
      eventTime: "2024-01-15T16:45:00Z"
      eventSource: rds.amazonaws.com
      eventName: ModifyDBInstance
      awsRegion: us-east-1
      sourceIPAddress: "10.0.2.100"
      userAgent: "aws-cli/2.13.0"
      requestParameters:
        dBInstanceIdentifier: "production-db"
        publiclyAccessible: true
      errorCode: AccessDenied
      errorMessage: "User is not authorized to perform: rds:ModifyDBInstance"
      requestID: "e5f6a7b8-c9d0-1234-ef01-234567890bcd"
      eventID: "j5i6h7g8-f9e0-1234-5678-901234efghij"
      readOnly: false
      eventType: AwsApiCall
      managementEvent: true
      recipientAccountId: "123456789012"
      eventCategory: Management

Detection logic

Condition

eventSource eq "rds.amazonaws.com"
eventName in ["ModifyDBInstance", "ModifyDBCluster"]
errorCode is_null
requestParameters.publiclyAccessible eq "True"

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
`errorCode`	is_null	(no value, null check)
`eventName`	in	`ModifyDBCluster` `ModifyDBInstance`
`eventSource`	eq	`rds.amazonaws.com`
`requestParameters.publiclyAccessible`	eq	`True`

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
`eventName`
`eventSource`
`awsRegion`
`recipientAccountId`
`sourceIPAddress`
`userAgent`
`userIdentity`
`dBInstanceIdentifier`	`requestParameters.dBInstanceIdentifier`
`userName`	`userIdentity.userName`

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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)