What Are Denial-of-Service (DoS) Attacks?

What Are Denial-of-Service Attacks

DoS attacks are commonly employed by hackers to steal intellectual property, disrupt business operations and gain competitive edge. Signs of DoS attacks often include non-malicious performance and availability issues like an increase in traffic volume.

DoS attacks often employ floods of bandwidth-saturating packets that overwhelm a target’s connection bandwidth and resources, leaving their targets defenseless against further attacks. To effectively combat DoS attacks, organizations should establish baselines of normal network activity against which any sudden increases or decreases in performance can be measured against.

What Is a Denial-of-Service DoS Attack?

DoS attacks aim to restrict legitimate users from accessing your network resources, be they slowing network performance, blocking critical applications or making web-based services unusable.

Threat actors use DoS attacks as a diversion while engaging in unlawful activity – such as stealing data or launching ransomware attacks – against your organization. They also employ them to gain a competitive edge or damage your reputation.

DoS attacks use fraudulent requests that overwhelm the target server with too many requests to process. They may come from one system (known as SYN flooding) or many systems all working simultaneously from different locations (known as Distributed Denial of Service Attack, or DDoS).

DDoS attacks typically employ thousands of Internet users who combine to send small requests that together overload a target server. Participants could either be willing accomplices – for instance members of loosely organized illegal hacktivist groups – or unwitting victims whose computers have been infiltrated with malware.

How does a DoS attack work?

DoS attacks work by overwhelming a targeted computer with requests until normal traffic has been blocked, rendering websites or services inoperable for users while making business operations harder for companies to maintain.

Criminal hackers often launch DoS attacks for various reasons, including revenge or hacktivism, but also as an attempt to cause financial losses to businesses by disrupting or crashing their web servers, or as an extortion scheme against victims.

As part of their defense against DoS attacks, cybersecurity professionals employ various tools and techniques, such as filtering information before it reaches Web pages – these filters look for certain patterns or identifiers within information that they then block out before reaching servers’ Web pages.

Cybercriminals who employ sophisticated attack techniques often utilize botnets – networks of compromised computers that harvest their processing power to execute an attack – as an additional weapon against targets. Such networks allow attackers to launch multiple simultaneous attacks at once – potentially overwhelming them completely. Hackers conceal their identity using IP spoofing techniques which alter attack packet sources’ IP addresses.

Signs of a DoS attack

DoS attacks create disruptions that prevent employees and customers from accessing email, websites and online accounts, costing organizations both time, money and resources to recover from. Hackers often conduct DoS attacks for various reasons – to show off their hacking abilities to others or gain recognition among peers; or perhaps to achieve social or political goals such as hacktivism where attacks may be launched against companies they deem engaging in activities they consider violating their views.

DDoS attacks have become more frequent with people’s growing reliance on digital platforms for communication and transacting, while being easier for attackers to execute due to renting botnets of infected computers at a nominal fee from almost anywhere. DDoS attacks can fill finite server capacities with meaningless requests that overwhelm finite server capacities like flooding attacks like SYN flood that brought down GitHub in 2019 or DYNDNS attack against CNN in 2018, as well as application-layer attacks like Slowloris that flood web servers with connections but never submit complete requests so legitimate users cannot access sites as an attack occurs preventing legitimate users from accessing them.

1. common historic DoS attacks

Since the dawn of mainframe-timeshare systems, hackers have used multiple user systems as platforms for denial-of-access attacks by flooding it with false requests that overwhelm available bandwidth and slow or block services.

ICMP floods, more commonly known as smurf attacks, take advantage of misconfigured network devices by sending out an overwhelming surge of pings that each use a different IP address – inundating each device until they cannot process normal traffic flow and eventually shutting down altogether.

SYN flood attacks rely on flooding the server by making half-open connections, forcing it to devote resources exclusively to fulfilling half-opened requests instead of accommodating legitimate ones. This prevents additional legitimate requests from reaching their target, leaving the server unavailable for new customers and rendering it inaccessible.

Hacktivists may also employ their skills to launch DoS attacks for social or political gain, either to show off their hacking capabilities or as part of a wider campaign against an organization they find objectionable – for instance, those opposing whaling could launch DoS attacks against all companies involved in that industry.

2. Smurf attack

Cybercriminals use malware to send network packets with fake source addresses that contain an Internet Control Message Protocol (ICMP) echo request, prompting other devices in the network to send back ping replies back at that source address, overloading its server temporarily or permanently and forcing its closure.

Smurf attacks may not be as prevalent, but when successful they can be extremely harmful. Customers could become disgruntled about website availability or services unavailable online and an overwhelming flood of ICMP echo requests can overload server resources to the point that functionalities cease working properly altogether.

One of the first Smurf attacks occurred against the University of Minnesota in 1999 and resulted in its temporary shutdown for several days. Since then, attacks like these have continued to deface websites and disrupt businesses, leading to lost revenues and data losses. To protect themselves against such threats, companies must invest in adequate cyber security solutions and infrastructure, with redundancy spread among multiple data centers providing added bandwidth and protection against Smurf attacks.

3. Ping flood

Ping Flood (ICMP, Internet Control Message Protocol) Flood Attack is one of the most frequently employed denial-of-service attacks by hackers, taking advantage of the ubiquitous PING functionality used for network availability checks. An attacker will employ multiple IP echo request packets and Reverberation Answer Packets from an attacker server and flood their target with them, thus using up valuable bandwidth resources while blocking legitimate traffic from reaching its intended destinations.

Ping flood attacks can be performed over any connection – from direct to one-to-one connections and routers alike – as long as the victim device’s IP address is known. Mitigation measures include restricting ping requests and their acceptance rates, but attackers can still use these floods to map networks, identify vulnerable systems and gather intelligence on organizations. Ping floods have even been used by attackers as a prescheduled event disrupter such as university websites publishing grade results online; potentially leading to unintended DoS attacks or even DOS attacks! Also used by attackers before more targeted attacks are launched upon specific systems before more specific attacks are launched against it launching more targeted assaults on systems before proceeding further with more targeted assaults on this type of system before going after more targeted attacks with more direct methods of attacks against a system before further targeting more targeted attacks by testing its resilience before launch more targeted attacks on it.

4. Ping of Death

ICMP (Internet Control Message Protocol) allows you to easily check if another machine is online by sending out packets and waiting for responses; if no reply comes back then that means they are offline and hacker can use this process against them in an effort to take down websites or network devices.

To launch this attack, an attacker simply needs to select an IP address and send large ping packets sequentially to it – no detailed knowledge of computer systems is necessary! ICMP packets can also be used as weapons against machines if desired; just ensure these attacks have a suitable source.

Modern devices and software are equipped to protect against Ping of Death attacks. Adjustments made to hardware and server software help ward off attacks like this by verifying packet sizes don’t exceed when joining IP fragments together, while larger memory buffers reduce buffer overflow risks. Often these measures are enough to block such threats from infiltrating company networks.

Difference between a DDoS attack and a DOS attack

DDoS attacks typically use networks of infected computers, IoT devices and compromised machines (known as bots) controlled remotely by hackers – this group of devices that hackers command remotely is called a botnet.

DDoS attacks typically consist of many botnets flooding a server with traffic, making it impossible for the victim to access their website or other online services. DDoS perpetrators could be motivated by revenge, blackmail or hacktivism; and victims could suffer as a result of such criminal behavior.

DDoS attacks occur when hackers send fake IP data packets to network devices or webservers, forcing those devices to respond by flooding the network with requests that become overwhelming, often resulting in its crash and availability being interrupted. Common DDoS tactics include ICMP attacks, SYN floods and teardrop attacks – as well as amplified traffic generation techniques used by attackers that increase the volume generated from one source and thus target more victims quickly – though such attacks may be difficult to detect without an effective security suite in place.

Sam is an experienced information security specialist who works with enterprises to mature and improve their enterprise security programs. Previously, he worked as a security news reporter.