How a DoS attack worksA DoS attack prevents users from accessing a service by overwhelming either its physical resources or network connections. The attack essentially floods the service with so much traffic or data that no-one else can use it until the malicious flow has been handled. One way to overload a service's physical resources is to send it so many requests in such a short time that it overwhelms all the available memory, processing or storage space. In extreme cases, this may even lead to damage of the physical components for these resources. Similarly, to disrupt a service's network connections a DoS attack can send invalid, malformed, or just an overwhelming number of connection requests to it. While these are being addressed, connection requests from legitimate users can't be completed. Occasionally, a DoS attack exploits a vulnerability in a program or website to force improper use of its resources or network connections, which also leads to a denial of service. Some malware also include the ability to launch DoS attacks. When they infect a computer or device, these threats can use the resources of the infected machines to perform the attack. If multiple infected machines launch attacks against the same target, it's known as a Distributed-Denial-of-Service (DDoS)attack. The volume of data used in a DoS or DDoS attack can be huge, up to a rate of several gigabits per seconds. Botnets are quite often used to perform DDoS attacks, as many services do not have the resources needed to counter an attack from thousands, or even hundreds of thousands, of infected devices. For example, the largest known DDoS attack was the result of the 2016 Mirai botnet. DoS attack used for profitThere have been numerous cases of DoS attacks being launched for personal reasons — a grunge against a user, the service, or just pure mischief. Services under attack can be slowed or crashed for periods ranging from a few hours to a couple days. For many businesses, the forced downtime can result in significant disruption to their users, or even financial losses. Users trying to access a service that is under attack will usually perceive that it is either loading slowly, keeps getting disconnected, or can't connect at all. There have also been cases of DoS attacks that were launched because of corporate or political rivalry. Perhaps the most notable case of an attack that was attributed to political rivalry was the 2007 attacks on Estonia, in which many of the online resources of the Estonian government were targeted. Defending against a DoS attackLaunching a DoS attack used to require a certain level of technical knowledge and ability. This tended to limit their use to people who were skilled, or were able to find and hire someone with the necessary skills. Nowadays however, there are simple programs or tools available for sale in online criminal forums that allow even an unskilled user to launch a DoS attack. This had made such attacks much more feasible for criminals and other parties looking to disrupt an online service. The threat of being targeted by DoS attacks have lead many major online services to implement various strategies for handling overwhelming floods of data or traffic. Some of the anti-DoS techniques include:
For many smaller services however, such countermeasures can be prohibitively costly. If adequate defenses are not in place, simply restarting the service can be fruitless as long as it remains exposed to the same attack, causing it to crash again and again until the attack ceases. Protection and mitigation techniques using managed Distributed Denial of Service (DDoS) protection service, Web Access Firewall (WAF), and Content Delivery Network (CDN) A Denial of Service (DoS) attack is a malicious attempt to affect the availability of a targeted system, such as a website or application, to legitimate end users. Typically, attackers generate large volumes of packets or requests ultimately overwhelming the target system. In case of a Distributed Denial of Service (DDoS) attack, and the attacker uses multiple compromised or controlled sources to generate the attack. In general, DDoS attacks can be segregated by
which layer of the Open Systems Interconnection (OSI) model they attack. They are most common at the Network (layer 3), Transport (Layer 4), Presentation (Layer 6) and Application (Layer 7) Layers.
While thinking about mitigation techniques against these attacks, it is useful to group them as Infrastructure layer (Layers 3 and 4) and Application Layer (Layer 6 and 7) attacks. Infrastructure Layer Attacks Attacks at Layer 3 and 4, are typically categorized as Infrastructure layer attacks. These are also the most common type of DDoS attack and include vectors like synchronized (SYN) floods and other reflection attacks like User Datagram Packet (UDP) floods. These attacks are usually large in volume and aim to overload the capacity of the network or the application servers. But fortunately, these are also the type of attacks that have clear signatures and are easier to detect. Application Layer Attacks Attacks at Layer 6 and 7, are often categorized as Application layer attacks. While these attacks are less common, they also tend to be more sophisticated. These attacks are typically small in volume compared to the Infrastructure layer attacks but tend to focus on particular expensive parts of the application thereby making it unavailable for real users. For instance, a flood of HTTP requests to a login page, or an expensive search API, or even Wordpress XML-RPC floods (also known as Wordpress pingback attacks). Reduce Attack Surface Area One of the first techniques to mitigate DDoS attacks is to minimize the surface area that can be attacked thereby limiting the options for attackers and allowing you to build protections in a single place. We want to ensure that we do not expose our application or resources to ports, protocols or applications from where they do not expect any communication. Thus, minimizing the possible points of attack and letting us concentrate our mitigation efforts. In some cases, you can do this by placing your computation resources behind Content Distribution Networks (CDNs) or Load Balancers and restricting direct Internet traffic to certain parts of your infrastructure like your database servers. In other cases, you can use firewalls or Access Control Lists (ACLs) to control what traffic reaches your applications. Plan for Scale The two key considerations for mitigating large scale volumetric DDoS attacks are bandwidth (or transit) capacity and server capacity to absorb and mitigate attacks. Transit capacity. When architecting your applications, make sure your hosting provider provides ample redundant Internet connectivity that allows you to handle large volumes of traffic. Since the ultimate objective of DDoS attacks is to affect the availability of your resources/applications, you should locate them, not only close to your end users but also to large Internet exchanges which will give your users easy access to your application even during high volumes of traffic. Additionally, web applications can go a step further by employing Content Distribution Networks (CDNs) and smart DNS resolution services which provide an additional layer of network infrastructure for serving content and resolving DNS queries from locations that are often closer to your end users. Server capacity. Most DDoS attacks are volumetric attacks that use up a lot of resources; it is, therefore, important that you can quickly scale up or down on your computation resources. You can either do this by running on larger computation resources or those with features like more extensive network interfaces or enhanced networking that support larger volumes. Additionally, it is also common to use load balancers to continually monitor and shift loads between resources to prevent overloading any one resource. Know what is normal and abnormal traffic Whenever we detect elevated levels of traffic hitting a host, the very baseline is to be able only to accept as much traffic as our host can handle without affecting availability. This concept is called rate limiting. More advanced protection techniques can go one step further and intelligently only accept traffic that is legitimate by analyzing the individual packets themselves. To do this, you need to understand the characteristics of good traffic that the target usually receives and be able to compare each packet against this baseline. Deploy Firewalls for Sophisticated Application attacks A good practice is to use a Web Application Firewall (WAF) against attacks, such as SQL injection or cross-site request forgery, that attempt to exploit a vulnerability in your application itself. Additionally, due to the unique nature of these attacks, you should be able to easily create customized mitigations against illegitimate requests which could have characteristics like disguising as good traffic or coming from bad IPs, unexpected geographies, etc. At times it might also be helpful in mitigating attacks as they happen to get experienced support to study traffic patterns and create customized protections.  Your account will be within the AWS Free Tier, which enables you to gain free, hands-on experience with the AWS platform, products, and services. All AWS customers benefit from the automatic protections of AWS Shield Standard, at no additional charge. AWS support for Internet Explorer ends on 07/31/2022. Supported browsers are Chrome, Firefox, Edge, and Safari. Learn more » What are the 3 types of DDoS attacks?Three broad types of DDoS attacks are as follows.. Application layer attacks. The application layer is where the server generates the response to an incoming client request. ... . Protocol attacks. ... . Volumetric attacks.. Which of the following is the example of DoS attack?Some common examples of DDoS attacks are UDP flooding, SYN flooding and DNS amplification.
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Which of the following attacks can also be used to perform denial of service (dos) attacks?
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