Stop DDoS Attacks Against your Website!

This is the reality and the impacts Distributed Denial of Service (DDoS) attacks have on your websites and their associated server resources. A DoS/DDoS can happen within seconds / minutes and the impacts can be devastating. The impacts will range from less severe issues like down time, to getting banned by your host for Terms of Service (ToS) violations. This doesn’t account for the economic impacts to your business (i.e., downtime = no purchases, no availability).

Understanding a [Distributed] Denial of Service (DoS / DDoS) Attack

Denial of Service (DoS) attacks and Distributed Denial of Service (DDoS) attacks are the same thing, only thing differentiating the two is scale. When you hear someone mention a DoS attack, you can expect the attack to be marginal (Qualifier: obviously marginal is very subjective and many would disagree that any DoS is marginal). In most instances, when you hear someone say DDoS, you can think the opposite (i.e., think grand!).

Whether a DoS or DDoS attack, the attacker is making use of one or more computers. DoS attacks are on the lower end of that spectrum while DDoS attacks are on the higher end of it, very large DDoS attacks can span 100’s if not 1,000’s of systems. The proliferation of DoS/DDoS attacks are directly attributed to the proliferation of DDoS-For-Hire service market, also known as Booter Services.

An attacker that is leveraging a Denial of Service (DoS) attack method has one goal in mind, to disrupt your websites performance. They disrupt your website performance by making it slow to respond to legitimate requests or disabling the website entirely, making it impossible for legitimate users to access your website. This type of disruption, depending on your configuration, can be devastating to your business.

There are three main DDoS / DoS attack types:

Each of these attacks types are designed to consume your web server resources, in one way or another and each have the same outcome – your web server / website slow to a halt or crash.

1. Volume Based DoS Attacks

As the name implies, this type of attacks depends on volume. The attacker employs a basic tactic, more resources wins this game. If they can overload your resources, they win. For most everyday website owners, this is an easy win. Most website owners are leveraging everyday Shared hosts and those with VPS environments are often configured in the smallest tiers and configurations.

2. Protocol Based DoS Attacks

The internet is all based on protocols, it’s how things get from point A to point B. This type of attack can include things likes Ping of Death, SYN Flood, Packet modifications and number of other variations.

 

3. Application Layer Attacks

The basis for this attack is often targeting applications like Web Servers (i.e., Windows IIS, Apache, etc…), but more and more we’re seeing this type of attack evolve to application platforms like WordPress, Joomla and other similar applications.

Website Firewall Protects Against DDoS / DoS Attacks

There are a number of DoS / DDoS attacks that we, Sucuri, deal with on a daily basis. These are the ones that the Sucuri Website Firewall will protect your website against:

1. HTTP Flood Attack

This type of Layer 7 application attack happens when an attacker makes use of standard GET / POST requests in effort to overload your web servers response ability. This attack is also known as a volumetric attack, it doesn’t require malformed packets, spoofing or any variation of reflection techniques. This attack can occur over HTTP or HTTPS and is much easier to implement, making them the much preferred attack method, cheaper too, for a lot of booter services targeting websites. They can generate thousands of requests a second.

2. Simple Service Discovery Protocol (SSDP) DoS Attack

The Simple Service Discovery Protocol (SSDP) is often used for Plug & Play (UPnP) devices, and it was only in 2014 that we started to see DoS attacks leverage this protocol. It’s a relatively new attack vector for DoS attacks. It often targets traditional SSDP ports, (1900) and destination port 7 (echo). It’s a form of a UDP attack, which unlike SSDP is more common. The latest reports show that SSDP attacks have the ability to increase the amplification of the attack by 30 times which might explain why it’s being employed.

3. User Datagram Protocol (UDP) DoS Attack

The User Datagram Protocol (UDP) DoS attack will flood various ports on your web server, randomly, with packets – also known as Layer 3 / 4 attacks. This forces the web server to respond, in turn chewing through your web server resources forcing it to come to a halt or die completely. UDP is a connection-less protocol, meaning it doesn’t validate source IP addresses. It’s because of this that UDP attacks are often associated with Distributed Reflective Denial of Service (DRDoS) attacks.

4. Domain Name Server (DNS) Amplification DoS Attack

DNS Amplification DoS attacks are very popular today, they occur at Layers 3 / 4. They make use of publicly accessible DNS servers around the world to overwhelm your web server with DNS response traffic. Your web server is overwhelmed by the influx of responses in turn making it difficult to function as it’s resources are depleted, making it impossible to respond to legitimate DNS traffic.

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How to Launch a 65Gbps DDoS, and How to Stop One

How to Launch a 65Gbps DDoS, and How to Stop One

Yesterday I posted a post mortem on an outage we had Saturday. The outage was caused when we applied an overly aggressive rate limit to traffic on our network while battling a determined DDoS attacker. In the process of writing it I mentioned that we’d seen a 65Gbps DDoS earlier on Saturday. I’ve received several questions since that all go something like: “65Gbps DDoS!? Who launches such an attack and how do you defend yourself against it?!” So I thought I’d give a bit more detail.

What Constitutes a Big DDoS?

A 65Gbps DDoS is a big attack, easily in the top 5% of the biggest attacks we see. The graph below shows the volume of the attack hitting our EU data centers (the green line represents inbound traffic). When an attack is 65Gbps that means every second 65 Gigabits of data is sent to our network. That’s the equivalent data volume of watching 3,400 HD TV channels all at the same time. It’s a ton of data. Most network connections are measured in 100Mbps, 1Gbps or 10Gbps so attacks like this would quickly saturate even a large Internet connection.

How to Launch a 65Gbps DDoS, and How to Stop One

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How are amplification lists scanned?

A key question that was recently asked quite a bit is how amplification lists (which are used for UDP amplification) are scanned. The most common ones are SSDP, DNS, NTP, CHARGEN and SNMP. There are a lot of possible UDP based services that can be used for packet amplification but only a few provide a good amplification rate.

The most common method to scan for amplification lists is using a scanner. Which means sending a packet to every possible IP and save only the ones with a good amplification rate.

Another method is a honeypot method which consists on having a server with a high port speed (10Gbps), and using booters or stressers to catch the packets, ending up with a list of IPs that were used for the stress test on a specific UDP service.