Denial-of-Service (DoS) Attack

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What Is a Denial-of-Service (DoS) Attack?
A denial-of-service (DoS) attack is an intentional cyberattack carried out on networks, websites, and online resources to restrict access to its legitimate users. This is usually done by overloading the target network or site with fake system requests, preventing legitimate users from accessing it, sometimes crashing or damaging a system outright. DoS attacks may last anywhere from a few hours to many months.

A common type of DoS attack that is prevalent on the web is called the distributed denial-of-service (DDoS) attack that relies on infected computers or devices from around the world in a coordinated effort to block access.

KEY TAKEAWAYS

• A denial-of-service (DoS) is a form of cyberattack that prevents a rightful user from accessing a computer system, platform, or website.
• In a DoS attack, rapid and continuous online requests are sent to a target server in order to overload the server’s bandwidth.
• Distributed denial-of-service (DDoS) attacks leverage a wide web of computers or devices infected with malware that launch a coordinated barrage of meaningless online requests, blocking legitimate access.

How Denial-of-Service Attacks Work
DoS attacks are on the rise because as businesses and consumers use more digital platforms in communicating and transacting with each other, these cyberattacks target digital intellectual property and infrastructures. Cyberattacks are typically launched to steal personally identifiable information (PII), causing considerable damages to the businesses’ financial pockets and reputations. Data breaches can target a specific company or a host of companies at the same time. A company with high-security protocols in place may be attacked through a member of its supply chain with inadequate security measures. When multiple companies have been selected for an attack, the perpetrators can use a DoS approach.

In a DoS attack, the cyberattackers typically use one internet connection and one device to send rapid and continuous requests to a target server to overload the server’s bandwidth. DoS attackers exploit a software vulnerability in the system and proceed to exhaust the RAM or CPU of the server. The damage in loss of service done by a DoS attack can be fixed in a short time by implementing a firewall with allow and deny rules. Since a DoS attack only has one IP address, the IP address can be easily fished out and denied further access using a firewall. However, there is a type of DoS attack that is not so easy to detect—a distributed denial of-service (DDoS) attack.

Distributed Denial-of-Service (DDoS) Attack
A distributed denial-of-service (DDoS) attack uses multiple infected devices and connections spread around the world as a botnet. A botnet is a network of personal devices that have been compromised by cybercriminals without the knowledge of the owners of the devices. The hackers infect the computers with malicious software to gain control of the system to send spam and fake requests to other devices and servers. A target server that falls victim to a DDoS attack will experience an overload due to the hundreds or thousands of phony traffic that comes in. Because the server is attacked from multiple sources, detecting all the addresses from these sources may prove difficult. Separating legitimate traffic from the fake traffic may also be impossible to do, hence, another reason why it is hard for a server to withstand a DDoS attack.

Unlike most cyberattacks that are initiated to steal sensitive information, initial DDoS attacks are launched to make websites inaccessible to their users. However, some DDoS attacks are used as a facade for other malicious acts. When servers have been successfully knocked down, the culprits may go behind the scenes to dismantle the websites’ firewalls or weaken their security codes for future attack plans.

A DDoS attack can also be used as a digital supply chain attack. If the cyberattackers cannot penetrate the security systems of their multiple target websites, they can find a weak link that is connected to all the targets and attack the link instead. When the link is compromised, the primary targets would automatically be indirectly affected as well.

DDoS Attack Example
In October 2016, a DDoS attack was carried out on a domain name system (DNS) provider, Dyn. Think of a DNS as the internet’s directory that routes your request or traffic to the intended webpage. A company like Dyn hosts and manages the domain name of select companies in this directory on its server. When Dyn’s server is compromised, this also affects the websites of the companies that it hosts. The 2016 attack on Dyn flooded its servers with an overwhelming amount of internet traffic, thereby creating a massive web outage and shutting down over 80 websites including major sites like Twitter, Amazon, Spotify, Airbnb, PayPal, and Netflix.

Some of the traffic was detected from a botnet created with malicious software known as Mirai that seemed to have affected over 500,000 devices connected to the internet.2 Unlike other botnets that capture private computers, this particular botnet gained control over the easily accessible Internet of Things (IoT) devices such as DVRs, printers, and cameras. These weakly secured devices were then used to make a DDoS attack by sending an insurmountable number of requests to Dyn’s server.

Cyber vandals keep coming up with new ways to commit cybercrime either for fun or profit. It is imperative that every device that has access to the internet has security protocols in place to restrict access.

(c) https://www.investopedia.com/terms/d/denial-service-attack-dos.asp

 

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DDoS attacks 101​

Cybercrime is expected to cost businesses more than $ 8 trillion over the next three years, according to a Juniper Research study.
But while large-scale phishing and ransomware attempts make many businesses concerned about online security, there is another type of cyberattack that is increasingly being used by adversaries. We are referring, of course, to DDoS attacks.
Distributed denial-of-service (DDoS) attacks are one of the oldest existing methods of attack.
They can damage the company's network and / or website servers long enough to significantly disable it, or even cause it to stop working for the duration of the attack and some time after it.
For many industries-whether it's e-Commerce, banking, or healthcare – a well-executed DDoS attack can cause financial losses, reputational damage, and business closures.
But how much do you really understand DDoS attacks?
Knowing that they are a form of cyber attack or that they can cause damage is key to success, so keep reading to find out how they work, who is at risk, and what can be done to detect and mitigate them.

What is a DDoS attack?
DDoS attacks are malicious attempts to distort the normal traffic patterns of a service, network, or server by overloading the target with web traffic flow.
A DDoS attack increases efficiency by using multiple compromised servers, collectively referred to as botnets, as sources of malicious traffic.
Attacking devices may include PCs and other Internet resources, such as IOT devices.
DDoS attacks can occur at businesses of any size at any time and in any place, and in 2019, the number of attacks that companies around the world are exposed to is growing rapidly.
Recent examples of successful DDoS attacks include a high-profile attack on GitHub.
The code repository was disabled due to an attack that can scale up to 1.3 Tbit / s.

What happens during a DDoS attack?
DDoS requires attackers to gain access to a group of computers in order to launch an attack.
PCs and other machines (such as smartphones) are infected with malicious software, and the attack turns each of them into a zombie device or bot.
The enemy then gains remote control of the bots, creating a group known as a botnet.
Once a botnet is created, an attacker can instruct individual bots by sending updated instructions to each machine using the remote control method.
When a botnet targets a victim's network or service, each bot responds by sending multiple requests to the victim, which can cause the target machine's buffer to overflow, resulting in denial of service to normal traffic.
Since each bot is a legitimate machine, filtering out malicious traffic from regular traffic can be difficult.

What are the types of DDoS attacks?
The basis of a DDoS attack can vary significantly, but most attacks are usually classified into one of the following three categories.

Volume-based DDoS attacks
These attacks attempt to use up all available bandwidth between the target network / server and the rest of the Internet.
Examples of capacity-based DDoS attack vectors include increasing DNS, ICMP flooding, increasing NTP, and more.

Protocol-based DDoS attacks
DDoS attacks, also called TCP state exhaustion attacks, target the capacity of the state tables of infrastructure components such as load balancers and firewalls, as well as connection state tables on web application servers.
Attack vectors in this category include Ping of Death, SYN Flood, and more.

Application-level DDoS attacks
Application-level attacks attempt to exhaust the resources of a service or application at layer 7 (components are present at layer seven of the OSI model).
This is usually done by attacking the application layer at the point where web pages are created and transmitted in response to an HTTP-related request.
Examples of application-level attacks include DNSQF (DNS Query Flood), HTTP Flooding, and attacks targeting other software vulnerabilities.

What are some common DDoS attack tools?
There are several tools that can be used to launch a DDoS attack.
Some of them serve legitimate purposes, as network engineers and security researchers can sometimes use them to test their companies ' security mechanisms.
Others are designed to attack a specific layer of the application stack.
Below is a compilation of the most commonly used options.

HULK (HTTP Unbearable Load King)
This DDoS attack tool creates a unique request for each received request in order to disrupt the flow of traffic to the victim's server.
It has an easily accessible list of random user agents that it uses to avoid detection by known patterns.
In addition, it uses referrer forgery in some cases and is able to bypass caching mechanisms to directly affect the system's resource pool.

LOIC (Low Orbit Ion Cannon)
This is an open source application that can be used to run DDoS attacks on small networks.
Атака выполняется путем отправки HTTP, TCP или UDP-запросов на целевой сервер.
LOIC был популярен у известной группой Anonymous, которая использовала его для разрушения сетей многих известных организаций.
Users just need to know the server's IP address or URL, and the tool will do the rest of the work.

HOIC (High Orbit Ion Cannon)
This is another popular tool for DDoS attacks.
HOIC uses the HTTP Protocol to perform a targeted attack that is difficult to detect and mitigate.
The software, however, requires at least 50 users running on their individual machines to launch a coordinated botnet attack.

What can I do to detect a DDoS attack?
There are several integrations that indicate an attack of this kind, for example, a SIEM solution that shows a huge spread of traffic.
For example, if a network usually receives 10,000 visitors on a Friday night, it may be a cause for alarm if it suddenly receives 50,000 pings from different sources.
You should also keep a close eye on any email accounts hosted on the company's server and the comment area of any sites running on this system.
A dramatic increase in the time-to-live echo request timeout (TTL), 503 errors, and IP address requests may indicate that it is time to strengthen security.