AWS EC2 Download Instance User Data

Severity: medium
Compliance: Stratus Red Team aws.discovery.ec2-download-user-data
Log types: AWS.CloudTrail
Tags: AWS CloudTrail, EC2, Discovery, Cloud Infrastructure Discovery, Discovery - Cloud Infrastructure Discovery
Reference: https://hackingthe.cloud/aws/general-knowledge/introduction_user_data/
Source: github.com/panther-labs/panther-analysis

An entity has accessed the user data scripts of multiple EC2 instances.

MITRE ATT&CK coverage

Tactic	Techniques
Discovery	`T1580` Cloud Infrastructure Discovery

Rule body yaml

AnalysisType: rule
Filename: aws_ec2_download_instance_user_data.py
RuleID: "AWS.EC2.DownloadInstanceUserData"
DisplayName: AWS EC2 Download Instance User Data
Enabled: true
LogTypes:
  - AWS.CloudTrail
Severity: Medium
Reports:
  MITRE ATT&CK:
    - TA0007:T1580 # Discovery: Cloud Infrastructure Discovery

  Stratus Red Team:
    - aws.discovery.ec2-download-user-data
Description: >
  An entity has accessed the user data scripts of multiple EC2 instances.
Threshold: 10
DedupPeriodMinutes: 1440
Reference: >
  https://hackingthe.cloud/aws/general-knowledge/introduction_user_data/
Runbook: |
  An entity has accessed the user data scripts of multiple EC2 instances. This is
  often an attempt to find unsecured credentials. Ensure the EC2 instances accessed
  do not have any sensitive information stored in the user data.

  Cloud security scanning tools may trigger false positives.  Add an exclude filter for
  the scanning tool's service account to prevent false positives.
SummaryAttributes:
  - userAgent
  - sourceIpAddress
  - recipientAccountId
  - p_any_aws_instance_ids
Tags:
  - AWS CloudTrail
  - EC2
  - Discovery
  - Cloud Infrastructure Discovery
  - Discovery - Cloud Infrastructure Discovery
Tests:
  - Name: Unsuccessful Attempt
    ExpectedResult: true
    Log:
      {
        "p_event_time": "2024-12-11 21:49:07.000000",
        "p_log_type": "AWS.CloudTrail",
        "p_parse_time": "2024-12-11 21:55:54.289594",
        "awsRegion": "us-west-2",
        "errorCode": "Client.UnauthorizedOperation",
        "errorMessage": "You are not authorized to perform this operation. User: arn:aws:sts::111122223333:assumed-role/SampleRole/sample-session is not authorized to perform: ec2:DescribeInstanceAttribute on resource: arn:aws:ec2:us-west-2:111122223333:instance/* because no identity-based policy allows the ec2:DescribeInstanceAttribute action. Encoded authorization failure message: 2RCBDBB0PcDpowyBFV7UpJobr-4iGb1MWqjKES--SAO_ca79pxBjKLQQ-sBGm2_m8jjcTAITBlNRa1WCVabq3VCghw9mbj0XZ3-2ZfsVyUrQWiTSUqYh9CUFVnWOmp710QzzKLj-Dy5Aup-bkSCbadoQe6HMevGPiSGeklgwBQc4jLO3oIbPTsujAijnaVr4CUIRBkD4KI8H2ZshEgJOujlpkg47FYqU8bVPNEIv9OwsQ9g4dRMB_cJ7C43kpURWIuiWkFpN8Q84RubskMNB3IfkHGR_Y63Z3LLzOCbPgT4S2zt97PBryCs-lUWSdA2ZCq9dcOtoHQq3Ed-3eB4o7FdZ0cJawa2i6oeUGzzPC2JtBQBcCqExMS8CXENosA0LY9cRUOSo4xc439wzlNpUbMI6K_y1AZWWN0f1QzLW1GkhtlUaLZFvLTwMqTVhClznln2ntmAJ_6iVVlvYco5x6Z4oNn8pMVPk76Iq8yM9o_2-tXmt0st7y_9B83eTSFOTbRnwgHabQXuMyzFKAA3xtuMcbcpB-Ij8c70lkv-eVQeJnfqRd_zbbnsMhxBybfjQyirKjY8bfLg",
        "eventCategory": "Management",
        "eventID": "fa67e0b9-9837-4c84-baa0-78a271821d3e",
        "eventName": "DescribeInstanceAttribute",
        "eventSource": "ec2.amazonaws.com",
        "eventTime": "2024-12-11 21:49:07.000000000",
        "eventType": "AwsApiCall",
        "eventVersion": "1.10",
        "managementEvent": true,
        "readOnly": true,
        "recipientAccountId": "111122223333",
        "requestID": "f2362cc7-4396-4be5-950c-16c36dddde76",
        "requestParameters": {
          "attribute": "userData",
          "instanceId": "i-12345678"
        },
        "sourceIPAddress": "1.2.3.4",
        "tlsDetails": {
          "cipherSuite": "TLS_AES_128_GCM_SHA256",
          "clientProvidedHostHeader": "ec2.us-west-2.amazonaws.com",
          "tlsVersion": "TLSv1.3"
        },
        "userAgent": "sample-user-agent",
        "userIdentity": {
          "accessKeyId": "SAMPLE_ACCESS_KEY",
          "accountId": "111122223333",
          "arn": "arn:aws:sts::111122223333:assumed-role/SampleRole/sample-session",
          "principalId": "SAMPLE_PRINCIPAL_ID:sample-session",
          "sessionContext": {
            "attributes": {
              "creationDate": "2024-12-11T21:49:04Z",
              "mfaAuthenticated": "false"
            },
            "sessionIssuer": {
              "accountId": "111122223333",
              "arn": "arn:aws:iam::111122223333:role/SampleRole",
              "principalId": "SAMPLE_PRINCIPAL_ID",
              "type": "Role",
              "userName": "SampleRole"
            }
          },
          "type": "AssumedRole"
        }
      }
  - Name: Successful Attempt
    ExpectedResult: true
    Log:
      {
        "p_event_time": "2024-12-12 21:44:35.000000",
        "p_log_type": "AWS.CloudTrail",
        "p_parse_time": "2024-12-12 21:50:54.711099",
        "awsRegion": "us-west-2",
        "eventCategory": "Management",
        "eventID": "6dbc00d3-1230-492a-ad34-4e3e49aba847",
        "eventName": "DescribeInstanceAttribute",
        "eventSource": "ec2.amazonaws.com",
        "eventTime": "2024-12-12 21:44:35.000000000",
        "eventType": "AwsApiCall",
        "eventVersion": "1.10",
        "managementEvent": true,
        "readOnly": true,
        "recipientAccountId": "111122223333",
        "requestID": "26b6b895-900d-44aa-b286-b8d828c31aed",
        "requestParameters": {
          "attribute": "userData",
          "instanceId": "i-1234567890abcdefa"
        },
        "sourceIPAddress": "1.2.3.4",
        "tlsDetails": {
          "cipherSuite": "TLS_AES_128_GCM_SHA256",
          "clientProvidedHostHeader": "ec2.us-west-2.amazonaws.com",
          "tlsVersion": "TLSv1.3"
        },
        "userAgent": "sample-user-agent",
        "userIdentity": {
          "accessKeyId": "SAMPLE_ACCESS_KEY",
          "accountId": "111122223333",
          "arn": "arn:aws:sts::111122223333:assumed-role/SampleRole/sample-session",
          "principalId": "SAMPLE_PRINCIPAL_ID:sample-session",
          "sessionContext": {
            "attributes": {
              "creationDate": "2024-12-12T21:43:11Z",
              "mfaAuthenticated": "false"
            },
            "sessionIssuer": {
              "accountId": "111122223333",
              "arn": "arn:aws:iam::111122223333:role/SampleRole",
              "principalId": "SAMPLE_PRINCIPAL_ID",
              "type": "Role",
              "userName": "SampleRole"
            }
          },
          "type": "AssumedRole"
        }
      }
  - Name: Panther Cloud Security Scanning
    ExpectedResult: false
    Log:
      {
        "p_log_type": "AWS.CloudTrail",
        "awsRegion": "us-west-2",
        "eventCategory": "Management",
        "eventID": "21764f21-382a-4863-8573-908558a839ab",
        "eventName": "DescribeInstanceAttribute",
        "eventSource": "ec2.amazonaws.com",
        "eventTime": "2025-02-09 20:29:17.000000000",
        "eventType": "AwsApiCall",
        "eventVersion": "1.10",
        "managementEvent": true,
        "readOnly": true,
        "recipientAccountId": "123412341234",
        "requestID": "cb8b2a56-d76d-40c2-af25-58c1547d9a48",
        "requestParameters": {
          "attribute": "userData",
          "instanceId": "i-1234123412341234"
        },
        "sourceIPAddress": "cloudformation.amazonaws.com",
        "userAgent": "cloudformation.amazonaws.com",
        "userIdentity": {
          "accountId": "123412341234",
          "arn": "arn:aws:sts::123412341234:assumed-role/PantherAuditRole-us-east-1/12341234123412341234",
          "invokedBy": "cloudformation.amazonaws.com",
          "principalId": "AROA1234123412341234:12341234123412341234",
          "sessionContext": {
            "attributes": {
              "creationDate": "2025-02-09T20:29:15Z",
              "mfaAuthenticated": "false"
            },
            "sessionIssuer": {
              "accountId": "123412341234",
              "arn": "arn:aws:iam::123412341234:role/PantherAuditRole-us-east-1",
              "principalId": "AROA1234123412341234",
              "type": "Role",
              "userName": "PantherAuditRole-us-east-1"
            }
          },
          "type": "AssumedRole"
        }
      }

Detection logic

Condition

eventName eq "DescribeInstanceAttribute"
requestParameters.attribute eq "userData"

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
`eventName`	eq	`DescribeInstanceAttribute`
`requestParameters.attribute`	eq	`userData`

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`
`actor_user`

`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)