A Denial of Service (DoS) is a a cyberattack where the perpetrator makes a device or system asset inaccessible to its legitimate users by disrupting its functionality or administration.
A DoS is commonly performed by flooding the focused-on device or asset — often a website on the Internet — with pointless demands trying to over-burden systems and keep some or all legitimate requests from being satisfied.
In a Distributed Denial of Service (DDoS), the low-value traffic that floods the victim with requests comes from a wide range of sources. This makes it difficult to stop a DDoS through the inability to detect or isolate a solitary source of the attack.
A DoS or DDoS assault closely resembles a gathering of individuals swarming the entryway of a shop, making it difficult for genuine clients to enter, consequently disrupting commerce.
DoS/DDoS assailants frequently target destinations or systems functioning on prominent web servers, for example banks or payment gateways. Retribution, extortion, mischief, or activism can serve as motivations for these attacks.
"The National Retail Federation has warned that some of their big-box members are seeing a lot of denial of service attacks. They're addressing this ahead of the holiday shopping season because these attacks can disrupt e-commerce by making the websites unavailable to shoppers."