AWS S3 Copy Object with Client-Side Encryption

Severity: medium
Compliance: Stratus Red Team aws.impact.s3-ransomware-client-side-encryption
Log types: AWS.CloudTrail
Tags: AWS, S3, CloudTrail, Ransomware, Impact:Data Destruction
Reference: https://docs.aws.amazon.com/AmazonS3/latest/userguide/logging-with-cloudtrail.html
Source: github.com/panther-labs/panther-analysis

This rule detects when objects are copied in an S3 bucket with client-side encryption. Such actions can be indicative of unauthorized data access or other suspicious activities.

MITRE ATT&CK coverage

Tactic	Techniques
Impact	No specific technique

Rules detecting the same action

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

AWS S3 Object Encryption Using External KMS Key (Elastic)

Rule body yaml

AnalysisType: rule
DedupPeriodMinutes: 60
DisplayName: AWS S3 Copy Object with Client-Side Encryption
Enabled: true
Filename: aws_s3_copy_object_with_client_side_encryption.py
RuleID: "AWS.S3.CopyObjectWithClientSideEncryption"
Severity: Medium
Threshold: 50
LogTypes:
  - AWS.CloudTrail
Tags:
  - AWS
  - S3
  - CloudTrail
  - Ransomware
  - Impact:Data Destruction
Reports:
  Stratus Red Team:
    - aws.impact.s3-ransomware-client-side-encryption
Description: >
  This rule detects when objects are copied in an S3 bucket with client-side encryption. Such actions can be indicative of unauthorized data access or other suspicious activities.
Runbook: |
  Investigate the user and the actions performed on the S3 bucket to ensure they were authorized. Unauthorized copying of encrypted objects can lead to data exposure.
  Steps to investigate:
  1. Identify the user who performed the action.
  2. Verify if the action was authorized.
  3. Check for any other suspicious activities performed by the same user.
  4. If unauthorized, take necessary actions to secure the S3 bucket and prevent further unauthorized access.
Reference: https://docs.aws.amazon.com/AmazonS3/latest/userguide/logging-with-cloudtrail.html
Tests:
  - Name: CopyObject with client-side encryption
    LogType: AWS.CloudTrail
    ExpectedResult: true
    Log:
      {
        "eventVersion": "1.08",
        "userIdentity": {
          "type": "IAMUser",
          "principalId": "EXAMPLE",
          "arn": "arn:aws:iam::123456789012:user/Alice",
          "accountId": "123456789012",
          "accessKeyId": "EXAMPLEKEY",
          "userName": "Alice"
        },
        "eventTime": "2023-10-01T12:34:56Z",
        "eventSource": "s3.amazonaws.com",
        "eventName": "CopyObject",
        "awsRegion": "us-east-1",
        "sourceIPAddress": "192.0.2.0",
        "userAgent": "aws-sdk-go/1.15.12 (go1.12.6; linux; amd64)",
        "requestParameters": {
          "bucketName": "example-bucket",
          "key": "example-object",
          "x-amz-server-side-encryption-customer-algorithm": "AES256"
        },
        "responseElements": null,
        "additionalEventData": {
          "SignatureVersion": "SigV4",
          "CipherSuite": "ECDHE-RSA-AES128-GCM-SHA256",
          "bytesTransferredIn": 0,
          "bytesTransferredOut": 0
        },
        "requestID": "EXAMPLE123456789",
        "eventID": "EXAMPLE-1234-5678-9012-EXAMPLE",
        "readOnly": false,
        "resources": [
          {
            "type": "AWS::S3::Object",
            "ARN": "arn:aws:s3:::example-bucket/example-object"
          }
        ],
        "eventType": "AwsApiCall",
        "managementEvent": false,
        "recipientAccountId": "123456789012",
        "sharedEventID": "EXAMPLE-1234-5678-9012-EXAMPLE",
        "vpcEndpointId": "vpce-1a2b3c4d"
      }
  - Name: CopyObject without client-side encryption
    LogType: AWS.CloudTrail
    ExpectedResult: false
    Log:
      {
        "eventVersion": "1.08",
        "userIdentity": {
          "type": "IAMUser",
          "principalId": "EXAMPLE",
          "arn": "arn:aws:iam::123456789012:user/Bob",
          "accountId": "123456789012",
          "accessKeyId": "EXAMPLEKEY",
          "userName": "Bob"
        },
        "eventTime": "2023-10-01T12:34:56Z",
        "eventSource": "s3.amazonaws.com",
        "eventName": "CopyObject",
        "awsRegion": "us-east-1",
        "sourceIPAddress": "192.0.2.0",
        "userAgent": "aws-sdk-go/1.15.12 (go1.12.6; linux; amd64)",
        "requestParameters": {
          "bucketName": "example-bucket",
          "key": "example-object"
        },
        "responseElements": null,
        "additionalEventData": {
          "SignatureVersion": "SigV4",
          "CipherSuite": "ECDHE-RSA-AES128-GCM-SHA256",
          "bytesTransferredIn": 0,
          "bytesTransferredOut": 0
        },
        "requestID": "EXAMPLE123456789",
        "eventID": "EXAMPLE-1234-5678-9012-EXAMPLE",
        "readOnly": false,
        "resources": [
          {
            "type": "AWS::S3::Object",
            "ARN": "arn:aws:s3:::example-bucket/example-object"
          }
        ],
        "eventType": "AwsApiCall",
        "managementEvent": false,
        "recipientAccountId": "123456789012",
        "sharedEventID": "EXAMPLE-1234-5678-9012-EXAMPLE",
        "vpcEndpointId": "vpce-1a2b3c4d"
      }

Detection logic

Condition

not (errorCode is_not_null or errorMessage is_not_null)
eventSource eq "s3.amazonaws.com"
eventName eq "CopyObject"
requestParameters.x-amz-server-side-encryption-customer-algorithm is_not_null

Exclusions

Top-level NOT(...) conjuncts: predicates this rule actively suppresses.

Field	Kind	Excluded values
`errorCode`	is_not_null	(no value, null check)
`errorMessage`	is_not_null	(no value, null check)

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
`eventName`	eq	`CopyObject`
`eventSource`	eq	`s3.amazonaws.com`
`requestParameters.x-amz-server-side-encryption-customer-algorithm`	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
`eventName`
`eventSource`
`awsRegion`
`recipientAccountId`
`sourceIPAddress`
`userAgent`
`userIdentity`
`actor_user`
`bucketName`	`requestParameters.bucketName`

`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)