AnalysisType: rule
Filename: aws_ec2_network_acl_modified.py
RuleID: "AWS.EC2.NetworkACLModified"
DisplayName: "EC2 Network ACL Modified"
Enabled: true
LogTypes:
- AWS.CloudTrail
Tags:
- AWS
- Security Control
- Defense Evasion:Impair Defenses
Reports:
CIS:
- 3.11
MITRE ATT&CK:
- TA0005:T1562
Severity: Info
Description: An EC2 Network ACL was modified.
Runbook: https://docs.runpanther.io/alert-runbooks/built-in-rules/aws-ec2-network-acl-modified
Reference: https://docs.aws.amazon.com/vpc/latest/userguide/vpc-network-acls.html#nacl-tasks
SummaryAttributes:
- eventName
- userAgent
- sourceIpAddress
- recipientAccountId
- p_any_aws_arns
Tests:
- Name: Network ACL Modified
ExpectedResult: true
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",
}
- Name: Network ACL Not Modified
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":
{
"sessionIssuer":
{
"type": "Role",
"principalId": "1111",
"arn": "arn:aws:iam::123456789012:role/tester",
"accountId": "123456789012",
"userName": "tester",
},
"webIdFederationData": {},
"attributes":
{
"mfaAuthenticated": "false",
"creationDate": "2019-01-01T00:00:00Z",
},
},
},
"eventTime": "2019-01-01T00:00:00Z",
"eventSource": "ec2.amazonaws.com",
"eventName": "DescribeNetworkAcls",
"awsRegion": "us-west-2",
"sourceIPAddress": "111.111.111.111",
"userAgent": "Mozilla",
"requestParameters":
{
"networkAclIdSet": {},
"filterSet":
{
"items":
[
{
"name": "vpc-id",
"valueSet": { "items": [{ "value": "vpc-1" }] },
},
],
},
},
"responseElements": null,
"requestID": "1",
"eventID": "1",
"eventType": "AwsApiCall",
"recipientAccountId": "123456789012",
}
- Name: Error Modifying Network ACL
ExpectedResult: false
Log:
{
"errorCode": "InvalidCharacter",
"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",
}
# ------ paired body: aws_ec2_network_acl_modified.py ------
from panther_aws_helpers import aws_cloudtrail_success, aws_rule_context
# API calls that are indicative of an EC2 Network ACL modification
EC2_NACL_MODIFIED_EVENTS = {
"CreateNetworkAcl",
"CreateNetworkAclEntry",
"DeleteNetworkAcl",
"DeleteNetworkAclEntry",
"ReplaceNetworkAclEntry",
"ReplaceNetworkAclAssociation",
}
def rule(event):
return aws_cloudtrail_success(event) and event.get("eventName") in EC2_NACL_MODIFIED_EVENTS
def dedup(event):
return event.get("recipientAccountId")
def alert_context(event):
return aws_rule_context(event)