Nov 19 2020
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AWS Network Firewall – New Managed Firewall Service in VPC

Our customers want to have a high availability, scalable firewall service to protect their virtual networks in the cloud. Security is the number one priority of AWS, which has provided various firewall capabilities on AWS that address specific security needs, like Security Groups to protect Amazon Elastic Compute Cloud (EC2) instances, Network ACLs to protect Amazon Virtual Private Cloud (VPC) subnets, AWS Web Application Firewall (WAF) to protect web applications running on Amazon CloudFront, Application Load Balancer (ALB) or Amazon API Gateway, and AWS Shield to protect against Distributed Denial of Service (DDoS) attacks.

We heard customers want an easier way to scale network security across all the resources in their workload, regardless of which AWS services they used. They also want customized protections to secure their unique workloads, or to comply with government mandates or commercial regulations. These customers need the ability to do things like URL filtering on outbound flows, pattern matching on packet data beyond IP/Port/Protocol and the ability to alert on specific vulnerabilities for protocols beyond HTTP/S.

Today, I am happy to announce AWS Network Firewall, a high availability, managed network firewall service for your virtual private cloud (VPC). It enables you to easily deploy and manage stateful inspection, intrusion prevention and detection, and web filtering to protect your virtual networks on AWS. Network Firewall automatically scales with your traffic, ensuring high availability with no additional customer investment in security infrastructure.

With AWS Network Firewall, you can implement customized rules to prevent your VPCs from accessing unauthorized domains, to block thousands of known-bad IP addresses, or identify malicious activity using signature-based detection. AWS Network Firewall makes firewall activity visible in real-time via CloudWatch metrics and offers increased visibility of network traffic by sending logs to S3, CloudWatch and Kinesis Firehose. Network Firewall is integrated with AWS Firewall Manager, giving customers who use AWS Organizations a single place to enable and monitor firewall activity across all your VPCs and AWS accounts. Network Firewall is interoperable with your existing security ecosystem, including AWS partners such as CrowdStrike, Palo Alto Networks, and Splunk. You can also import existing rules from community maintained Suricata rulesets.

Concepts of Network Firewall
AWS Network Firewall runs stateless and stateful traffic inspection rules engines. The engines use rules and other settings that you configure inside a firewall policy.

You use a firewall on a per-Availability Zone basis in your VPC. For each Availability Zone, you choose a subnet to host the firewall endpoint that filters your traffic. The firewall endpoint in an Availability Zone can protect all of the subnets inside the zone except for the one where it’s located.

You can manage AWS Network Firewall with the following central components.

  • Firewall – A firewall connects the VPC that you want to protect to the protection behavior that’s defined in a firewall policy. For each Availability Zone where you want protection, you provide Network Firewall with a public subnet that’s dedicated to the firewall endpoint. To use the firewall, you update the VPC route tables to send incoming and outgoing traffic through the firewall endpoints.
  • Firewall policy – A firewall policy defines the behavior of the firewall in a collection of stateless and stateful rule groups and other settings. You can associate each firewall with only one firewall policy, but you can use a firewall policy for more than one firewall.
  • Rule group – A rule group is a collection of stateless or stateful rules that define how to inspect and handle network traffic. Rules configuration includes 5-tuple and domain name filtering. You can also provide stateful rules using Suricata open source rule specification.

AWS Network Firewall – Getting Started
You can start AWS Network Firewall in AWS Management Console, AWS Command Line Interface (CLI), and AWS SDKs for creating and managing firewalls. In the navigation pane in VPC console, expand AWS Network Firewall and then choose Create firewall in Firewalls menu.

To create a new firewall, enter the name that you want to use to identify this firewall and select your VPC from the dropdown. For each availability zone (AZ) where you want to use AWS Network Firewall, create a public subnet to for the firewall endpoint. This subnet must have at least one IP address available and a non-zero capacity. Keep these firewall subnets reserved for use by Network Firewall.

For Associated firewall policy, select Create and associate an empty firewall policy and choose Create firewall.

Your new firewall is listed in the Firewalls page. The firewall has an empty firewall policy. In the next step, you’ll specify the firewall behavior in the policy. Select your newly created the firewall policy in Firewall policies menu.

You can create or add new stateless or stateful rule groups – zero or more collections of firewall rules, with priority settings that define their processing order within the policy, and stateless default action defines how Network Firewall handles a packet that doesn’t match any of the stateless rule groups.

For stateless default action, the firewall policy allows you to specify different default settings for full packets and for packet fragments. The action options are the same as for the stateless rules that you use in the firewall policy’s stateless rule groups.

You are required to specify one of the following options:

  • Allow – Discontinue all inspection of the packet and permit it to go to its intended destination.
  • Drop – Discontinue all inspection of the packet and block it from going to its intended destination.
  • Forward to stateful rule groups – Discontinue stateless inspection of the packet and forward it to the stateful rule engine for inspection.

Additionally, you can optionally specify a named custom action to apply. For this action, Network Firewall sends an CloudWatch metric dimension named CustomAction with a value specified by you. After you defined a named custom action, you can use it by name in the same context where you have define it. You can reuse a custom action setting among the rules in a rule group and you can reuse a custom action setting between the two default stateless custom action settings for a firewall policy.

After you’ve defined your firewall policy, you can insert the firewall into your VPC traffic flow by updating the VPC route tables to include the firewall.

How to set up Rule Groups
You can create new stateless or stateful rule groups in Network Firewall rule groups menu, and choose Create rule group. If you select Stateful rule group, you can select one of three options: 1) 5-tuple format, specifying source IP, source port, destination IP, destination port, and protocol, and specify the action to take for matching traffic, 2) Domain list, specifying a list of domain names and the action to take for traffic that tries to access one of the domains, and 3) Suricata compatible IPS rules, providing advanced firewall rules using Suricata rule syntax.

Network Firewall supports the standard stateless “5 tuple” rule specification for network traffic inspection with priority number that indicates the processing order of the stateless rule within the rule group.

Similarly, a stateful 5 tuple rule has the following match settings. These specify what the Network Firewall stateful rules engine looks for in a packet. A packet must satisfy all match settings to be a match.

A rule group with domain names has the following match settings – Domain name, a list of strings specifying the domain names that you want to match, and Traffic direction, a direction of traffic flow to inspect. The following JSON shows an example rule definition for a domain name rule group.

{ "RulesSource": { "RulesSourceList": { "TargetType": "FQDN_SNI","HTTP_HOST", "Targets": [ "test.example.com", "test2.example.com" ], "GeneratedRulesType": "DENYLIST" } } }

A stateful rule group with Suricata compatible IPS rules has all settings defined within the Suricata compatible specification. For example, as following is to detect SSH protocol anomalies. For information about Suricata, see the Suricata website.

alert tcp any any -> any 22 (msg:"ALERT TCP port 22 but not SSH"; app-layer-protocol:!ssh; sid:2271009; rev:1;)

You can monitor Network Firewall using CloudWatch, which collects raw data and processes it into readable, near real-time metrics, and AWS CloudTrail, a service that provides a record of API calls to AWS Network Firewall by a user, role, or an AWS service. CloudTrail captures all API calls for Network Firewall as events. To learn more about logging and monitoring, see the documentation.

Network Firewall Partners
At this launch, Network Firewall integrates with a collection of AWS partners. They provided us with lots of helpful feedback. Here are some of the blog posts that they wrote in order to share their experiences (I am updating this article with links as they are published).

Available Now
AWS Network Firewall is now available in US East (N. Virginia), US West (Oregon), and Europe (Ireland) Regions. Take a look at the product page, price, and the documentation to learn more. Give this a try, and please send us feedback either through your usual AWS Support contacts or the AWS forum for Amazon VPC.

Learn all the details about AWS Network Firewall and get started with the new feature today.

— Channy;

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