AWS S3 Unknown Requester

Severity: low
Compliance: Panther Data Access
Log types: AWS.S3ServerAccess
Tags: AWS, Configuration Required, Security Control, Collection:Data From Cloud Storage Object
Reference: https://docs.aws.amazon.com/AmazonS3/latest/userguide/walkthrough1.html
Source: github.com/panther-labs/panther-analysis

Validates that proper IAM entities are accessing sensitive data buckets.

MITRE ATT&CK coverage

Tactic	Techniques
Collection	`T1530` Data from Cloud Storage

Rule body yaml

AnalysisType: rule
Filename: aws_s3_unknown_requester_get_object.py
RuleID: "AWS.S3.ServerAccess.UnknownRequester"
DisplayName: "AWS S3 Unknown Requester"
DedupPeriodMinutes: 60 # 1 hour
Enabled: false
LogTypes:
  - AWS.S3ServerAccess
Tags:
  - AWS
  - Configuration Required
  - Security Control
  - Collection:Data From Cloud Storage Object
Reports:
  Panther:
    - Data Access
  MITRE ATT&CK:
    - TA0009:T1530
Severity: Low
Description: Validates that proper IAM entities are accessing sensitive data buckets.
Runbook: If the S3 access is not expected for this bucket, investigate the requester's other traffic.
Reference: https://docs.aws.amazon.com/AmazonS3/latest/userguide/walkthrough1.html
SummaryAttributes:
  - bucket
  - key
  - operation
  - userAgent
  - remoteip
  - requester
  - p_any_aws_arns
  - p_any_aws_account_ids
Tests:
  - Name: Expected Access
    ExpectedResult: false
    Log:
      {
        "bucketowner": "f16a9e81a6589df1c902c86f7982fd14a88787db",
        "bucket": "panther-bootstrap-processeddata-AF1341JAK",
        "time": "2020-02-14 00:53:48.000000000",
        "remoteip": "127.0.0.1",
        "requester": "arn:aws:sts::123456789012:assumed-role/panther-log-analysis-AthenaApiFunctionRole-1KK31J1/panther-athena-api",
        "requestid": "101B7403B9828743",
        "operation": "REST.GET.OBJECT",
        "key": "AWSLogs/o-wwwwwwgggg/234567890123/CloudTrail-Digest/ca-central-1/2020/02/14/234567890123_CloudTrail-Digest_ca-central-1_POrgTrail_us-east-1_20200214T001007Z.json.gz",
        "requesturi": "PUT /AWSLogs/o-wwwwwwgggg/234567890123/CloudTrail-Digest/ca-central-1/2020/02/14/234567890123_CloudTrail-Digest_ca-central-1_POrgTrail_us-east-1_20200214T001007Z.json.gz HTTP/1.1",
        "httpstatus": 200,
        "objectsize": 747,
        "totaltime": 110,
        "turnaroundtime": 20,
        "useragent": "aws-internal/3 aws-sdk-java/1.11.714 Linux/4.9.184-0.1.ac.235.83.329.metal1.x86_64 OpenJDK_64-Bit_Server_VM/25.242-b08 java/1.8.0_242 vendor/Oracle_Corporation",
        "hostid": "neRpT/AXRsS3LMBqq/wND59opwPRWWKn7F6evEhdbS99me5fyIXpVI/MMIn6ECgU1YZAqwuF8Bw=",
        "signatureversion": "SigV4",
        "ciphersuite": "ECDHE-RSA-AES128-SHA",
        "authenticationtype": "AuthHeader",
        "hostheader": "cloudtrail.s3.us-east-1.amazonaws.com",
        "tlsVersion": "TLSv1.2",
      }
  - Name: Unexpected Access
    ExpectedResult: true
    Log:
      {
        "bucketowner": "f16a9e81a6589df1c902c86f7982fd14a88787db",
        "bucket": "panther-bootstrap-processeddata-AF1341JAK",
        "time": "2020-02-14 00:53:48.000000000",
        "remoteip": "127.0.0.1",
        "requester": "arn:aws:iam::123456789012:user/jim-bob",
        "requestid": "101B7403B9828743",
        "operation": "REST.GET.OBJECT",
        "key": "AWSLogs/o-wwwwwwgggg/234567890123/CloudTrail-Digest/ca-central-1/2020/02/14/234567890123_CloudTrail-Digest_ca-central-1_POrgTrail_us-east-1_20200214T001007Z.json.gz",
        "requesturi": "PUT /AWSLogs/o-wwwwwwgggg/234567890123/CloudTrail-Digest/ca-central-1/2020/02/14/234567890123_CloudTrail-Digest_ca-central-1_POrgTrail_us-east-1_20200214T001007Z.json.gz HTTP/1.1",
        "httpstatus": 200,
        "objectsize": 747,
        "totaltime": 110,
        "turnaroundtime": 20,
        "useragent": "aws-internal/3 aws-sdk-java/1.11.714 Linux/4.9.184-0.1.ac.235.83.329.metal1.x86_64 OpenJDK_64-Bit_Server_VM/25.242-b08 java/1.8.0_242 vendor/Oracle_Corporation",
        "hostid": "neRpT/AXRsS3LMBqq/wND59opwPRWWKn7F6evEhdbS99me5fyIXpVI/MMIn6ECgU1YZAqwuF8Bw=",
        "signatureversion": "SigV4",
        "ciphersuite": "ECDHE-RSA-AES128-SHA",
        "authenticationtype": "AuthHeader",
        "hostheader": "cloudtrail.s3.us-east-1.amazonaws.com",
        "tlsVersion": "TLSv1.2",
      }
  - Name: Failed Request
    ExpectedResult: false
    Log:
      {
        "bucketowner": "f16a9e81a6589df1c902c86f7982fd14a88787db",
        "bucket": "panther-bootstrap-processeddata-AF1341JAK",
        "time": "2020-02-14 00:53:48.000000000",
        "errorcode": "AuthorizationHeaderMalformed",
        "remoteip": "127.0.0.1",
        "requestid": "101B7403B9828743",
        "operation": "REST.GET.OBJECT",
        "key": "AWSLogs/o-wwwwwwgggg/234567890123/CloudTrail-Digest/ca-central-1/2020/02/14/234567890123_CloudTrail-Digest_ca-central-1_POrgTrail_us-east-1_20200214T001007Z.json.gz",
        "requesturi": "PUT /AWSLogs/o-wwwwwwgggg/234567890123/CloudTrail-Digest/ca-central-1/2020/02/14/234567890123_CloudTrail-Digest_ca-central-1_POrgTrail_us-east-1_20200214T001007Z.json.gz HTTP/1.1",
        "httpstatus": 400,
        "objectsize": 747,
        "totaltime": 110,
        "turnaroundtime": 20,
        "useragent": "aws-internal/3 aws-sdk-java/1.11.714 Linux/4.9.184-0.1.ac.235.83.329.metal1.x86_64 OpenJDK_64-Bit_Server_VM/25.242-b08 java/1.8.0_242 vendor/Oracle_Corporation",
        "hostid": "neRpT/AXRsS3LMBqq/wND59opwPRWWKn7F6evEhdbS99me5fyIXpVI/MMIn6ECgU1YZAqwuF8Bw=",
        "signatureversion": "SigV4",
        "ciphersuite": "ECDHE-RSA-AES128-SHA",
        "authenticationtype": "AuthHeader",
        "hostheader": "cloudtrail.s3.us-east-1.amazonaws.com",
        "tlsVersion": "TLSv1.2",
      }
  - Name: Snowflake Request
    ExpectedResult: false
    Log:
      {
        "authenticationtype": "AuthHeader",
        "bucket": "panther-bootstrap-processeddata-AF1341JAK",
        "bucketowner": "f16a9e81a6589df1c902c86f7982fd14a88787db",
        "ciphersuite": "ECDHE-RSA-AES128-GCM-SHA256",
        "httpstatus": 200,
        "key": "logs/logdir/year%253D2020/month%253D09/day%253D30/hour%253D19/file.json.gz",
        "requesturi": "GET /logs/logdir/year%3D2020/month%3D09/day%3D30/hour%3D19/file.json.gz HTTP/1.1",
        "objectsize": 4063,
        "operation": "REST.GET.OBJECT",
        "remoteip": "127.0.0.1",
        "requester": "arn:aws:sts::123456789012:assumed-role/panther-snowflake-logprocessing-role-us-west-2/snowflake",
        "requestid": "101B7403B9828743",
        "signatureversion": "SigV4",
        "time": "2020-09-30 20:49:19.000000000",
        "tlsVersion": "TLSv1.2",
        "totaltime": 10,
        "turnaroundtime": 9,
        "useragent": "snowflake/1.0",
      }

Detection logic

Condition

errorcode is_null
operation eq "REST.GET.OBJECT"

This rule also runs imperative logic the parser cannot express as a filter; the conditions above are the structured part it could extract.

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)
`operation`	eq	`REST.GET.OBJECT`

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
`eventName`
`eventSource`
`awsRegion`
`recipientAccountId`
`sourceIPAddress`
`userAgent`
`userIdentity`
`bucket`

`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)