AWS EC2 Multi Instance Connect

Status: Experimental
Severity: informational
Group by: requestParameters.sSHPublicKey
Compliance: Stratus Red Team aws.lateral-movement.ec2-instance-connect
Log types: AWS.CloudTrail
Tags: AWS CloudTrail, Lateral Movement, Remote Services, SSH, Lateral Movement:Remote Services
Reference: https://stratus-red-team.cloud/attack-techniques/AWS/aws.lateral-movement.ec2-instance-connect/
Source: github.com/panther-labs/panther-analysis

Detect when an attacker pushes an SSH public key to multiple EC2 instances.

MITRE ATT&CK coverage

Tactic	Techniques
Lateral Movement	`T1021.005` Remote Services: VNC

Rule body yaml

AnalysisType: rule
Filename: aws_ec2_multi_instance_connect.py
RuleID: "AWS.EC2.MultiInstanceConnect"
DisplayName: AWS EC2 Multi Instance Connect
Enabled: true
LogTypes:
  - AWS.CloudTrail
Severity: Info
Reports:
  MITRE ATT&CK:
    - TA0008:T1021.005 # Lateral Movement: Remote Services: SSH

  Stratus Red Team:
    - aws.lateral-movement.ec2-instance-connect
Description: >
  Detect when an attacker pushes an SSH public key to multiple EC2 instances.
DedupPeriodMinutes: 60
Threshold: 2
Reference: >
  https://stratus-red-team.cloud/attack-techniques/AWS/aws.lateral-movement.ec2-instance-connect/
Runbook: |
  Followup with the actor to determine if the SSH key is genuine. Consider using a different SSH key for each instance.
SummaryAttributes:
  - p_any_actor_ids
  - p_any_aws_account_ids
  - p_any_aws_instance_ids
  - p_any_usernames
Tags:
  - AWS CloudTrail
  - Lateral Movement
  - Remote Services
  - SSH
  - Lateral Movement:Remote Services
Status: Experimental
Tests:
  - Name: Public SSH Key Sent Successfully - Counts Toward Threshold
    ExpectedResult: true
    Log:
      {
        "p_event_time": "2025-01-13 19:58:59.000000000",
        "p_log_type": "AWS.CloudTrail",
        "p_parse_time": "2025-01-13 20:05:54.575569351",
        "awsRegion": "us-west-2",
        "eventCategory": "Management",
        "eventID": "d6d05dd2-d03d-4dce-a88c-02b6a567d889",
        "eventName": "SendSSHPublicKey",
        "eventSource": "ec2-instance-connect.amazonaws.com",
        "eventTime": "2025-01-13 19:58:59.000000000",
        "eventType": "AwsApiCall",
        "eventVersion": "1.08",
        "managementEvent": true,
        "readOnly": false,
        "recipientAccountId": "111122223333",
        "requestID": "25eac5d1-cd24-4156-a49b-f2bf3a20ec9d",
        "requestParameters": {
          "instanceId": "i-abcdef01234567890",
          "instanceOSUser": "ec2-user",
          "sSHPublicKey": "ssh-ed25519 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX"
        },
        "responseElements": {
          "requestId": "25eac5d1-cd24-4156-a49b-f2bf3a20ec9d",
          "success": true
        },
        "sourceIPAddress": "1.2.3.4",
        "tlsDetails": {
          "cipherSuite": "TLS_AES_128_GCM_SHA256",
          "clientProvidedHostHeader": "ec2-instance-connect.us-west-2.amazonaws.com",
          "tlsVersion": "TLSv1.3"
        },
        "userAgent": "stratus-red-team_8b255a24-d33d-4750-bd4b-4007124741df",
        "userIdentity": {
          "accessKeyId": "SAMPLE_ACCESS_KEY",
          "accountId": "111122223333",
          "arn": "arn:aws:sts::111122223333:assumed-role/SampleRole/bobson.dugnutt",
          "principalId": "SAMPLE_PRINCIPAL_ID:bobson.dugnutt",
          "sessionContext": {
            "attributes": {
              "creationDate": "2025-01-13T19:21:25Z",
              "mfaAuthenticated": "false"
            },
            "sessionIssuer": {
              "accountId": "111122223333",
              "arn": "arn:aws:iam::111122223333:role/aws-reserved/sso.amazonaws.com/us-west-2/SampleRole",
              "principalId": "SAMPLE_PRINCIPAL_ID",
              "type": "Role",
              "userName": "SampleRole"
            },
            "webIdFederationData": {}
          },
          "type": "AssumedRole"
        }
      }
  - Name: Public SSH Key Sent Successfully to Same Instance - Also Counts
    ExpectedResult: true
    Log:
      {
        "p_event_time": "2025-01-13 19:58:59.000000000",
        "p_log_type": "AWS.CloudTrail",
        "p_parse_time": "2025-01-13 20:05:54.575569351",
        "awsRegion": "us-west-2",
        "eventCategory": "Management",
        "eventID": "d6d05dd2-d03d-4dce-a88c-02b6a567d889",
        "eventName": "SendSSHPublicKey",
        "eventSource": "ec2-instance-connect.amazonaws.com",
        "eventTime": "2025-01-13 19:58:59.000000000",
        "eventType": "AwsApiCall",
        "eventVersion": "1.08",
        "managementEvent": true,
        "readOnly": false,
        "recipientAccountId": "111122223333",
        "requestID": "25eac5d1-cd24-4156-a49b-f2bf3a20ec9d",
        "requestParameters": {
          "instanceId": "i-abcdef01234567890",
          "instanceOSUser": "ec2-user",
          "sSHPublicKey": "ssh-ed25519 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX"
        },
        "responseElements": {
          "requestId": "25eac5d1-cd24-4156-a49b-f2bf3a20ec9d",
          "success": true
        },
        "sourceIPAddress": "1.2.3.4",
        "tlsDetails": {
          "cipherSuite": "TLS_AES_128_GCM_SHA256",
          "clientProvidedHostHeader": "ec2-instance-connect.us-west-2.amazonaws.com",
          "tlsVersion": "TLSv1.3"
        },
        "userAgent": "stratus-red-team_8b255a24-d33d-4750-bd4b-4007124741df",
        "userIdentity": {
          "accessKeyId": "SAMPLE_ACCESS_KEY",
          "accountId": "111122223333",
          "arn": "arn:aws:sts::111122223333:assumed-role/SampleRole/bobson.dugnutt",
          "principalId": "SAMPLE_PRINCIPAL_ID:bobson.dugnutt",
          "sessionContext": {
            "attributes": {
              "creationDate": "2025-01-13T19:21:25Z",
              "mfaAuthenticated": "false"
            },
            "sessionIssuer": {
              "accountId": "111122223333",
              "arn": "arn:aws:iam::111122223333:role/aws-reserved/sso.amazonaws.com/us-west-2/SampleRole",
              "principalId": "SAMPLE_PRINCIPAL_ID",
              "type": "Role",
              "userName": "SampleRole"
            },
            "webIdFederationData": { }
          },
          "type": "AssumedRole"
        }
      }
  - Name: Public SSH Key Not Sent Successfully
    ExpectedResult: false
    Log:
      {
        "p_event_time": "2025-01-13 20:46:57.000000000",
        "p_log_type": "AWS.CloudTrail",
        "p_parse_time": "2025-01-13 20:55:54.194562429",
        "awsRegion": "us-west-2",
        "errorCode": "AccessDenied",
        "errorMessage": "User: arn:aws:sts::111122223333:assumed-role/SampleRole/bobson.dugnutt is not authorized to perform: ec2-instance-connect:SendSSHPublicKey on resource: arn:aws:ec2:us-west-2:111122223333:instance/i-abcdef01234567890 because no identity-based policy allows the ec2-instance-connect:SendSSHPublicKey action",
        "eventCategory": "Management",
        "eventID": "3ad527a2-8799-4561-8def-963a6dcdbbb5",
        "eventName": "SendSSHPublicKey",
        "eventSource": "ec2-instance-connect.amazonaws.com",
        "eventTime": "2025-01-13 20:46:57.000000000",
        "eventType": "AwsApiCall",
        "eventVersion": "1.08",
        "managementEvent": true,
        "readOnly": false,
        "recipientAccountId": "111122223333",
        "requestID": "cd8f31b6-a30f-4b14-a06a-3b41012228f3",
        "sourceIPAddress": "1.2.3.4",
        "tlsDetails": {
          "cipherSuite": "TLS_AES_128_GCM_SHA256",
          "clientProvidedHostHeader": "ec2-instance-connect.us-west-2.amazonaws.com",
          "tlsVersion": "TLSv1.3"
        },
        "userAgent": "stratus-red-team_95b154bb-bcb2-4582-82f4-b3dbb6cfc1d9",
        "userIdentity": {
          "accessKeyId": "SAMPLE_ACCESS_KEY",
          "accountId": "111122223333",
          "arn": "arn:aws:sts::111122223333:assumed-role/SampleRole/bobson.dugnutt",
          "principalId": "SAMPLE_PRINCIPAL_ID:bobson.dugnutt",
          "sessionContext": {
            "attributes": {
              "creationDate": "2025-01-13T20:46:53Z",
              "mfaAuthenticated": "false"
            },
            "sessionIssuer": {
              "accountId": "111122223333",
              "arn": "arn:aws:iam::111122223333:role/aws-reserved/sso.amazonaws.com/us-west-2/SampleRole",
              "principalId": "SAMPLE_PRINCIPAL_ID",
              "type": "Role",
              "userName": "SampleRole"
            },
            "webIdFederationData": {}
          },
          "type": "AssumedRole"
        }
      }
  - Name: Unrelated Event
    ExpectedResult: false
    Log:
      {
        "eventVersion": "1.05",
          "userIdentity":
            {
              "type": "AssumedRole",
              "principalId": "1111:tester",
              "arn": "arn:aws:sts::123456789012:assumed-role/tester",
              "accountId": "123456789012",
              "accessKeyId": "1",
              "sessionContext":
                {
                  "attributes":
                    {
                      "mfaAuthenticated": "true",
                      "creationDate": "2019-01-01T00:00:00Z",
                    },
                  "sessionIssuer":
                    {
                      "type": "Role",
                      "principalId": "1111",
                      "arn": "arn:aws:iam::123456789012:role/tester",
                      "accountId": "123456789012",
                      "userName": "tester",
                    },
                },
            },
          "eventTime": "2019-01-01T00:00:00Z",
          "eventSource": "ec2.amazonaws.com",
          "eventName": "CreateNetworkAclEntry",
          "awsRegion": "us-west-2",
          "sourceIPAddress": "111.111.111.111",
          "userAgent": "console.ec2.amazonaws.com",
          "requestParameters":
            {
              "networkAclId": "acl-1",
              "ruleNumber": 500,
              "egress": true,
              "ruleAction": "allow",
              "icmpTypeCode": {},
              "portRange": {},
              "aclProtocol": "-1",
              "cidrBlock": "0.0.0.0/0",
            },
          "responseElements": { "requestID": "1", "_return": true },
          "requestID": "1",
          "eventID": "1",
          "eventType": "AwsApiCall",
          "recipientAccountId": "123456789012",
        }

Detection logic

Condition

not (errorCode is_not_null or errorMessage is_not_null)
eventName eq "SendSSHPublicKey"

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	`SendSSHPublicKey`

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)