Denial Of Service Attack (DoS)

DEFINITION of 'Denial Of Service Attack (DoS)'

An intentional cyberattack carried out on networks, websites and online resources in order to restrict access to its legitimate users. Denial of Service (DoS) attacks is a highly noticeable event that may last from a few hours to many months. A type of DoS attack that is prevalent on the web is called the Distributed Denial of Service (DDoS) attack.

BREAKING DOWN 'Denial Of Service Attack (DoS)'

The number of cyberattacks that are targeting digital intellectual property and infrastructures are steadily rising as businesses and consumers use more digital platforms in communicating and transacting with each other. Cyberattacks are typically launched to steal personally identifiable information (PII), causing huge damages to the businesses’ financial pockets and reputation. 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 poor security measures. When multiple companies have been selected for an attack, the perpetrators can use a Denial of Service Attack (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 in order 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 – Distributed Denial of Service (DDoS) attack.

A Distributed Denial of Service (DDoS) attack uses multiple infected devices and connections that are distributed around the world as a botnet. A botnet is a network of personal devices which have been compromised by cybercriminals without the knowledge of the owners of the devices. The hackers infect the computers with malicious software in order 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 fake traffic that comes in. Because the server is attacked from multiple sources, detecting all the addresses from these sources may prove difficult. Also 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 façade 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 main targets would automatically be indirectly affected as well.

In October 2016, a DDoS attack was carried out on a domain name service (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 a malicious software known as Mirai that seemed to have affected over 500, 000 devices connected to the internet. Unlike other botnets that capture private computers, this particular botnet gained control over 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 have secure protocols in place to restrict access.