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2022 holiday DDoS protection guide

November 15th, 2022 No comments

The holiday season is an exciting time for many people as they get to relax, connect with friends and family, and celebrate traditions. Organizations also have much to rejoice about during the holidays (for example, more sales for retailers and more players for gaming companies). Unfortunately, cyber attackers also look forward to this time of year to celebrate an emerging holiday tradition—distributed denial-of-service (DDoS) attacks.

While DDoS attacks happen all year round, the holidays are one of the most popular times and where some of the most high-profile attacks occur. Last October in India, there was a 30-fold increase in DDoS attacks targeting services frequently used during the festive season, including media streaming, internet phone services, and online gaming1. Last October through December, Microsoft mitigated several large-scale DDoS attacks, including one of the largest attacks in history from approximately 10,000 sources spanning multiple countries2.

Bar chart showing the number of DDoS attacks and duration distribution from March 2021-May 2022.
Figure 1. Number of DDoS attacks and duration distribution3

While retail and gaming companies are the most targeted during the holidays, organizations of all sizes and types are vulnerable to DDoS attacks. It’s easier than ever to conduct an attack. For only $500, anyone can pay for a DDoS subscription service to launch a DDoS attack. Every year, DDoS attacks are also becoming harder to protect against as new attack vectors emerge and cybercriminals leverage more advanced techniques, such as AI-based attacks.

With the holidays coming up, we’ve prepared this guide to provide you with an overview of DDoS attacks, trends we are seeing, and tips to help you protect against DDoS attacks.

What is a DDoS attack and how does it work?

A DDoS attack targets websites and servers by disrupting network services and attempts to overwhelm an application’s resources. Attackers will flood a site or server with large amounts of traffic, resulting in poor website functionality or knocking it offline altogether. DDoS attacks are carried out by individual devices (bots) or network of devices (botnet) that have been infected with malware and used to flood websites or services with high volumes of traffic. DDoS attacks can last a few hours, or even days.

What are the motives for DDoS attacks?

There is a wide range of motives behind DDoS attacks, including financial, competitive advantage, or political. Attackers will hold a site’s functionality hostage demanding payment to stop the attacks and get sites and serves back online. We’re seeing a rise in cybercriminals combining DDoS attacks with other extortion attacks like ransomware (known as triple extortion ransomware) to extort more pressure and command higher payouts. Politically motivated attacks, also known as “hacktivism”, are becoming more commonly used to disrupt political processes. At the start of the war in Ukraine earlier in 2022, the Ukrainian government reported the worst DDoS attack in history as attackers aimed to take down bank and government websites4.  Also, cybercriminals will often use DDoS attacks as a distraction for more sophisticated targeted attacks, including malware insertion and data exfiltration.

Why are DDoS attacks so common during the holidays?

Organizations typically have reduced resources dedicated to monitoring their networks and applications—providing easier opportunities for threat actors to execute an attack. Traffic volume is at an all-time high, especially for e-commerce websites and gaming providers, making it harder for IT staff to distinguish between legitimate and illegitimate traffic. For attackers seeking financial gain, the opportunity for more lucrative payouts can be higher during the holidays as revenues are at the highest and service uptime is critical. Organizations are more willing to pay to stop an attack to minimize loss of sales, customer dissatisfaction, or damage to their reputation.

Why protect yourself from DDoS attacks?

Any website or server downtime during the peak holiday season can result in lost sales and customers, high recovery costs, or damage to your reputation. The impact is even more significant for smaller organizations as it is harder for them to recover from an attack. Beyond the holidays when traffic is traditionally the highest, ongoing protection is also important. In 2021, the day with the most recorded attacks was August 10, indicating that there could be a shift toward year-round attacks2.

Tips for protecting and responding against DDoS attacks

  1. Don’t wait until after an attack to protect yourself. While you cannot completely avoid being a target of a DDoS attack, proactive planning and preparation can help you more effectively defend against an attack.
    • Identify the applications within your organization that are exposed to the public internet and evaluate potential risks and vulnerabilities.
    • It’s important that you understand the normal behavior of your application so that you’re prepared to act if the application is not behaving as expected. Azure provides monitoring services and best practices to help you gain insights on the health of your application and diagnose issues.
    • We recommend running attack simulations to test how your services will respond to an attack. You can simulate a DDoS attack on your Azure environment with services from our testing partners—BreakingPoint Cloud and RedButton.
  2. Make sure you’re protected. With DDoS attacks at an all-time high during the holidays, you need a DDoS protection service with advanced mitigation capabilities that can handle attacks at any scale.
    • We recommend enabling Azure DDoS Protection, which provides always-on traffic monitoring to automatically mitigate an attack when detected, adaptive real time tuning that compares your actual traffic against predefined thresholds, and full visibility on DDoS attacks with real-time telemetry, monitoring, and alerts.
    • Azure DDoS Protection should be enabled for virtual networks with applications exposed over the public internet. Resources in a virtual network that require protection against DDoS attacks include Azure Application Gateway, Azure Load Balancer, Azure Virtual Machines, and Azure Firewall.
    • For comprehensive protection against different types of DDoS attacks, set up a multi-layered defense by deploying Azure DDoS Protection with Azure Web Application Firewall (WAF). Azure DDoS Protection protects the network layer (Layer 3 and 4), and Azure WAF protects the application layer (Layer 7). You receive a discount on Azure WAF when deploying DDoS Network Protection along with Azure WAF, helping to reduce costs.
    • Azure DDoS Protection identifies and mitigates DDoS attacks without any user intervention. To get notified when there’s an active mitigation for a protected public IP resource, you can configure alerts.
  3. Create a DDoS response strategy. Having a response strategy is critical to help you identify, mitigate, and quickly recover from DDoS attacks. A key part of the strategy is a DDoS response team with clearly defined roles and responsibilities. This DDoS response team should understand how to identify, mitigate, and monitor an attack and be able to coordinate with internal stakeholders and customers. We recommend using simulation testing to identify any gaps in your response strategy.
  4. Reach out for help during an attack. If you think you are experiencing an attack, you should reach out to the appropriate technical professionals for help. Azure DDoS Protection customers have access to the DDoS Rapid Response (DRR) team, who can help with attack investigation during an attack as well as post-attack analysis. Check out this guide for more details on when and how to engage with the DRR team during an active attack.
  5. Learn and adapt after an attack. While you’ll likely want to move on as quickly as possible if you’ve experienced an attack, it’s important to continue to monitor your resources and conduct a retrospective after an attack. You should apply any learnings to improve your DDoS response strategy.

Azure offers cloud native, Zero Trust based network security solutions to protect your valuable resources from evolving threats. Azure DDoS Protection provides advanced, cloud-scale protection to defend against the largest and most sophisticated DDoS attacks.

Don’t let DDoS attacks ruin your holidays! Prepare for the upcoming holiday season with this guide and make sure Azure DDoS Protection is at the top of your holiday shopping list.

References

1Thirty-fold increase in DDoS cyber attacks in India in festive season, CIO News, ET CIO (indiatimes.com)

2Azure DDoS Protection—2021 Q3 and Q4 DDoS attack trends

3Microsoft Digital Defense Report 2022

4Ukraine says it suffered worst DDoS Attack in Standoff

Additional resources

Azure DDoS Protection reference architectures

Components of a DDoS response strategy

Azure DDoS Protection fundamental best practices

Azure network security resources

The post 2022 holiday DDoS protection guide appeared first on Microsoft Security Blog.

Anatomy of a DDoS amplification attack

Amplification attacks are one of the most common distributed denial of service (DDoS) attack vectors. These attacks are typically categorized as flooding or volumetric attacks, where the attacker succeeds in generating more traffic than the target can process, resulting in exhausting its resources due to the amount of traffic it receives. 

In this blog, we start by surveying the anatomy and landscape of amplification attacks, while providing statistics from Azure on most common attack vectors, volumes, and distribution. We then describe some of the countermeasures taken in Azure to mitigate amplification attacks. 

DDoS amplification attacks, what are they? 

Reflection attacks involve three parties: an attacker, a reflector, and a target. The attacker spoofs the IP address of the target to send a request to a reflector (e.g., open server, middlebox) that responds to the target, a virtual machine (VM) in this case. For the attack to be amplified the response should be larger than the request, resulting in a reflected amplification attack. The attacker’s motivation is to create the largest reflection out of the smallest requests. Attackers achieve this goal by finding many reflectors and crafting the requests that result in the highest amplification. 

The diagram illustrates how the attacker pushes a reflection attack to a target virtual machine that is hosted in Azure.
Figure 1. Reflected amplification attack

The root cause for reflected amplification attacks is that an attacker can force reflectors to respond to targets by spoofing the source IP address. If spoofing was not possible, this attack vector would be mitigated. Lots of effort has thus been made on disabling IP source address spoofing, and many organizations prevent spoofing nowadays so that attackers cannot leverage their networks for amplification attacks. Unfortunately, a significant number of organizations still allow source spoofing. The Spoofer project shows that a third of the IPv4 autonomous systems allow or partially allow spoofing.  

UDP and TCP amplification attacks 

Most attackers utilize UDP to launch amplification attacks since reflection of traffic with spoofed IP source address is possible due to the lack of proper handshake.  

While UDP makes it easy to launch reflected amplification attacks, TCP has a 3-way handshake that complicates spoofing attacks. As a result, IP source address spoofing is restricted to the start of the handshake. Although the TCP handshake allows for reflection, it does not allow for easy amplification since TCP SYN+ACK response is not larger than TCP SYN. Moreover, since the TCP SYN+ACK response is sent to the target, the attacker never receives it and can’t learn critical information contained in the TCP SYN+ACK needed to complete the 3-way handshake successfully to continue making requests on behalf of the target. 

The diagram illustrates how an attacker conducts a reflection attack in TCP. The attacker sends through SYN, then the reflector reflects packets restransmitted through SYN + ACK combination, which then sends an out-of-state SYN + ACK attack to the target virtual device.
Figure 2. Reflection attack in TCP 

In recent years, however, reflection and amplification attacks based on TCP have started emerging.  

Independent research found newer TCP reflected amplification vectors that utilize middleboxes, such as nation-state censorship firewalls and other deep packet inspection devices, to launch volumetric floods. Middleboxes devices may be deployed in asymmetric routing environments, where they only see one side of the TCP connection (e.g., packets from clients to servers). To overcome this asymmetry, such middleboxes often implement non-compliant TCP stack. Attackers take advantage of this misbehavior – they do not need to complete the 3-way handshake. They can generate a sequence of requests that elicit amplified responses from middleboxes and can reach infinite amplification in some cases. The industry has started witnessing these kinds of attacks from censorship and enterprise middle boxes, such as firewalls and IDPS devices, and we expect to see this trend growing as attackers look for more ways to create havoc utilizing DDoS as a primary weapon.  

Carpet bombing is another example of a reflected amplification attack. It often utilizes UDP reflection, and in recent years TCP reflection as well. With carpet bombing, instead of focusing the attack on a single or few destinations, the attacker attacks many destinations within a specific subnet or classless inter-domain routing (CIDR) block (for example /22). This will make it more difficult to detect the attack and to mitigate it, since such attacks can fly below prevalent baseline-based detection mechanisms. 

This diagram shows how an attacker uses reflectors to send spoofed packets to many target devices within a specific subnet hosted in Azure.
Figure 3. Carpet bombing attack 

One example of TCP carpet bombing is TCP SYN+ACK reflection, where attacker sends spoofed SYN to a wide range of random or pre-selected reflectors. In this attack, amplification is a result of reflectors that retransmit the TCP SYN+ACK when they do not get a response. The amplification of the TCP SYN+ACK response itself may not be large, and it depends on the number of retransmissions sent by the reflector. In Figure 3, the reflected attack traffic towards each of the target virtual machines (VMs) may not be enough to bring them down, however, collectively, the traffic may well overwhelm the targets’ network. 

UDP and TCP amplification attacks in Azure 

In Azure, we continuously work to mitigate inbound (from internet to Azure) and outbound (from Azure to internet) amplification attacks. In the last 12 months, we mitigated approximately 175,000 UDP reflected amplification attacks. We monitored more than 10 attack vectors, where the most common ones are NTP with 49,700 attacks, DNS with 42,600 attacks, SSDP with 27,100 attacks, and Memcached with 18,200 attacks. These protocols can demonstrate amplification factors of up to x4,670, x98, x76 and x9,000 respectively. 

This pie chart shows the volume of UDP- reflected amplification attacks observed in Azure from April 1, 2021, to March 31, 2022. The highest volume observed is 28% through NTP, while the least volume observed is 2% through Open VPN.
Figure 4. UDP reflected amplification attacks observed from April 1, 2021, to March 31, 2022

We measured the maximum attack throughput in packets per second for a single attack across all attack vectors. The highest throughput was a 58 million packets per second (pps) SSDP flood in August last year, in a short attack campaign that lasted 20 minutes on a single resource in Azure. 

This bar chart shows the packets per second flooding observed from April 1, 2021, to March 31, 2022 in Azure. The tallest bar represents the maximum observed throughput of 58 million packets per second SSDP flooding, while the shortest bar represents below 10M packets per second CharGEN flooding.
Figure 5. Maximum pps recorded for a single attack observed from April 1, 2021, to March 31, 2022 

TCP reflected amplification attacks are becoming more prevalent, with new attack vectors discovered. We encounter these attacks on Azure resources utilizing diverse types of reflectors and attack vectors. 

One such example is a TCP reflected amplification attack of TCP SYN+ACK on an Azure resource in Asia. Attack reached 30 million pps and lasted 15 minutes. Attack throughput was not high, however there were approximately 900 reflectors involved, each with retransmissions, resulting in a high pps rate that can bring down the host and other network infrastructure elements. 

This line chart shows the TCP SYN+ACK amplification attack volume on a single resource as seen on Azure. The line chart shows a spike reaching 30 million packets per second with a 15 minute duration. The 15-minute window illustrates the packets per second volume going down in the middle of the 15-minute window, and tapers off abruptly at the end of the 15-minute window.
Figure 6. TCP SYN+ACK amplification attack volume on an Azure resource in Asia

We see many TCP SYN+ACK retransmissions associated with the reflector that doesn’t get the ACK response from the spoofed source. Here is an example of such a retransmission: 

This screenshot shows a TCP SYN+ACK retransmission that doesn't get the ACK response. The screenshot highlights the information from source to destination and through which protocol it passes.

The retransmitted packet was sent 60 seconds after the first. 

Mitigating amplification attacks in Azure 

Reflected amplification attacks are here to stay and pose a serious challenge for the internet community. They continue to evolve and exploit new vulnerabilities in protocols and software implementations to bypass conventional countermeasures. Amplification attacks require collaboration across the industry to minimize their effect. It is not enough to mitigate such attacks at a certain location, with a pinpoint mitigation strategy. It requires intertwining of network and DDoS mitigation capabilities. 

Azure’s network is one of the largest on the globe. We combine multiple DDoS strategies across our network and DDoS mitigation pipeline to combat reflected amplification DDOS attacks.  

On the network side, we continuously optimize and implement various traffic monitoring, traffic engineering and quality of service (QoS) techniques to block reflected amplification attacks right at the routing infrastructure. We implement these mechanisms at the edge and core of our wide area networks (WAN) network, as well as within the data centers. For inbound traffic (from the Internet), it allows us to mitigate attacks right at the edge of our network. Similarly, outbound attacks (those that originate from within our network) will be blocked right at the data center, without exhausting our WAN and leaving our network. 

On top of that, our dedicated DDoS mitigation pipeline continuously evolves to offer advanced mitigation techniques against such attacks. This mitigation pipeline offers another layer of protection, on top of our DDoS networking strategies. Together, these two protection layers provide comprehensive coverage against the largest and most sophisticated reflected amplification attacks.  

Since reflected amplification attacks are typically volumetric, it is not only enough to implement advanced mitigation strategies, but also to maintain a highly scalable mitigation pipeline to be able to cope with the largest attacks. Our mitigation pipeline can mitigate more than 60Tbps globally, and we continue to evolve it by adding mitigation capacity across all network layers.  

Different attack vectors require different treatment 

UDP-based reflected amplification attacks are tracked, monitored, detected, and mitigated for all attack vectors. There are various mitigation techniques to combat these attacks, including anomaly detection across attacked IP addresses, L4 protocols, and tracking of spoofed source IPs. Since UDP reflected amplification attacks often create fragmented packets, we monitor IP fragments to mitigate them successfully.  

TCP-based reflected amplification attacks take advantage of poor TCP stack implementations, and large set of reflectors and targets, to launch such attacks. We adopt our mitigation strategies to be able to detect and block attacks from attackers and reflectors. We employ a set of mitigations to address TCP SYN, TCP SYN+ACK, TCP ACK, and other TCP-based attacks. Mitigation combines TCP authentication mechanisms that identify spoofed packets, as well as anomaly detection to block attack traffic when data is appended to TCP packets to trigger amplification with reflectors.  

The diagram shows how Azure uses mechanisms to stop amplification attacks as soon as a packet leaves a reflector or an attacker. Azure stops spoofed attacks in the following areas: 1. Attacks coming from an attacker-controlled reflector or direct from the attacker that is located outside Azure-protected space, with the attacks going to a target virtual machine or a reflector located inside a Azure; 2. Attacks coming from an attacker located within the Azure-protected space, and the attack is going to the reflector device outside of Azure, or an attack going through a reflector device to target another virtual machine.
Figure 7. Amplification attack detection 

Get started with Azure DDoS Protection to protect against amplification attacks 

Azure’s DDoS mitigation platform mitigated the largest ever DDoS attacks in history by employing a globally distributed DDoS protection platform that scales beyond 60Tbps. We ensure our platform and customers’ workloads are always protected against DDoS attacks. To enhance our DDoS posture, we continuously collaborate with other industry players to fight reflected amplification attacks. 

Azure customers are protected against Layer 3 and Layer 4 DDoS attacks as part of protecting our infrastructure and cloud platform. However, Azure DDoS Protection Standard provides comprehensive protection for customers by auto-tuning the detection policy to the specific traffic patterns of the protected application. This ensures that whenever there are changes in traffic patterns, such as in the case of flash crowd event, the DDoS policy is automatically updated to reflect those changes for optimal protection. When a reflected amplification attack is launched against a protected application, our detection pipeline detects it automatically based on the auto-tuned policy. The mitigation policy, that is automatically set for customers, without their need to manually configure or change it, includes the needed countermeasures to block reflected amplification attacks. 

Protection is simple to enable on any new or existing virtual network and does not require any application or resource changes. Our recently released Azure built-in policies allow for better management of network security compliance by providing great ease of onboarding across all your virtual network resources and configuration of logs. 

To strengthen the security posture of applications, Azure’s network security services can work in tandem to secure your workloads, where DDoS protection is one of the tools we provide. Organizations that pursue zero trust architecture can benefit from our services to achieve better protection. 

Learn more about Azure DDoS Protection Standard 

Amir Dahan and Syed Pasha
Azure Networking Team

References 

1 The Spoofer project 

2 Weaponizing Middleboxes for TCP Reflected Amplification 

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