A Distributed Denial-of-Service (DDoS) attack is a malicious attempt to disrupt the performance of an organization’s server, service, or network by overwhelming it with internet traffic. Some DDoS attacks focus on crashing a server, while others target the entire network, making all connected systems unreachable.
A DDoS attack launches its assault from multiple compromised computer systems, which makes it difficult to block. The goal isn’t usually to steal data, but to knock a service offline. However, cybercriminals sometimes use DDoS attacks as a smokescreen. While security teams battle to contain the surge, attackers attempt to break into the company to steal data and other valuable assets.
Falling victim to such an attack can be devastating. Extended business interruption, financial loss, and unhappy customers are just some of the consequences.
To help you understand the nature of this threat, we explore how DDoS attacks work and share strategies to identify, prevent, and mitigate them.
How Does a DDoS Attack Work?
Let’s break down the typical mechanics of a distributed denial-of-service attack.
Reliability and uptime
The first step in a DDoS attack involves a bad actor creating a botnet. This is a network of internet-connected devices, often dispersed, or “distributed”, across several locations.
Common devices exploited to create botnets include computers, mobile phones, and IoT tech like CCTV cameras, smart fridges, thermostats, toys, and Wi-Fi routers. The rise of IoT gadgets, many of which have minimal built-in security, has made it easier for hackers to build large botnets and launch successful DDoS attacks.
Command to flood the target
Once the botnet is assembled, the botmaster sends commands to all the compromised devices. These commands instruct the bots to simultaneously flood a specific target (the victim’s server, website, or network) with a massive volume of requests or connection attempts.
The broad goal is always the same: Denial of Service. The target’s network infrastructure, servers, and applications are so swamped by the deluge that they can no longer respond to legitimate network traffic. This achieves the attacker’s objective, which in practice might mean:
- Website unavailability: Users cannot access your website.
- Slow performance: Services become incredibly sluggish, which is important because Google Insights shows 53% of visitors will leave a mobile website if it takes longer than 3 seconds to load.
- Service outages: Applications and online services completely crash.
- Financial loss: Your company loses revenue, reputation, and customer trust
Inserting the botnet
The botnet malware is inserted into devices via various methods, including:
- Phishing emails: Phishing deceives victims into clicking on malicious links or attachments that install malware. This is the most common tactic.
- Exploiting software vulnerabilities: Hackers take advantage of unpatched security flaws in operating systems or applications.
- Drive-by downloads: Malware installs silently when users visit compromised or malicious websites.
- Trojan software: Seemingly legitimate apps or files secretly carry botnet malware.
- Weak credentials and brute force attacks: Attackers guess or crack weak passwords to gain access and install malware.
Many of these operations are automated, which means they are carried out cheaply and at scale.
Once the device is infected, the owner no longer has exclusive control of their phone or laptop. The compromised device is now what’s called a “bot” or “zombie”. The attacker (also known as the botmaster or bot herder) is able to remotely control the system without the owner’s knowledge.
In this way, a botnet of hundreds, thousands, even millions of zombie devices is assembled.
The defining characteristics of a botnet are:
- Scale: To provide the volume of traffic needed to overwhelm a target.
- Distribution: The idea is to make the operation hard to trace and mitigate. For this reason, the botnet might comprise IP addresses distributed across multiple geographical locations.
- Resilience: If some bots are taken offline, the attack can continue with the remaining ones.
DoS attack vs DDoS attack: What’s the difference?
DoS attack vs DDoS attack: What’s the difference?
We should briefly clarify the difference between a Denial-of-Service (DoS) attack and a Distributed Denial-of-Service (DDoS) attack because the terms are sometimes used interchangeably. Both have the same end goal: to overload and disrupt an IT system, network, or service with a flood of fake traffic.
The main difference lies in scale and complexity. A denial-of-service attack is less powerful and more easily defended than a DDoS attack. While DDoS hits the target system from numerous devices and locations, a DoS operation originates from a single system or IP address, making the disruption easier to identify and counter.
The Motivations for DDoS Attacks
Not all DDoS attacks are equal. Motivation is one of the key distinctions that sets these incidents apart. But what motivates individuals to launch DDoS attacks?
Here are the most common reasons:
- Political and consumer activism: Hacktivist groups use DDoS disruption as a form of protest. They typically target government agencies they ideologically oppose, or corporations they believe are acting unethically.
- Extortion: Cybercriminals launch these attacks to extort businesses. They demand ransom payments to halt the attack.
- Cyberwarfare: DDoS operations are a weapon of cyberwarfare. Government-authorized attacks may target another nation’s critical assets, such as state websites or power grids.
- Mischievous hackers: Many distributed denial-of-service attacks have been perpetrated by teenage hackers. They do it for the thrill and challenge, and even out of boredom.
- Business sabotage: Companies initiate DDoS attacks against rival businesses to render their online services unavailable, especially during high-stakes periods like Cyber Monday. Disgruntled employees also sometimes attempt to cripple their company’s operations using DoS or DDoS tactics.
The Motivations for DDoS Attacks
To appreciate the diversity of motivations and targets, here are examples of notable DDoS attacks:
- Estonia (2007): A politically motivated cyberattack against the Estonian government crippled banking and media websites.
- Mirai Botnet (2016): The Mirai malware hijacked hundreds of thousands of IoT devices to perpetrate a record-breaking assault. This “volumetric” DDoS attack disrupted major websites like Twitter, Netflix, and Reddit.
- US Banks attacks (2012–2013): A hacker group launched large-scale DDoS attacks on major U.S. financial institutions, including JPMorgan Chase and Bank of America. In recent years, financial institutions have been increasingly targeted by DDoS attacks.
- Google attack (2017, revealed in 2020): Google disclosed in 2020 that it mitigated a 2.54 Tbps DDoS attack in 2017. It’s believed this was carried out by government-sponsored hackers.
- GitHub attack (2018): GitHub was hit with one of the largest recorded DDoS attacks at the time (1.35 Tbps), briefly compromising the platform’s availability.
How Do You Identify a DDoS Attack?
While the outcome of a DDoS strike is unmistakable (your server crashed, or your applications grind to a halt), identifying a developing attack isn’t always straightforward.
This is because its symptoms often mimic routine technical issues like traffic spikes and server problems.
The best advice is to fully understand what abnormal system behavior looks like. Then check for a combination of symptoms that suggest significant deviations from the norm.
Here are the biggest warning indicators to watch for:
Unexplained drop in system performance
This is often the first and most noticeable sign.
- Unusually slow network performance: Your website, applications, or internal systems become unusually sluggish for no reason. Transactions are delayed, and data transfers crawl.
- Intermittent website or service unavailability: Your website goes offline sporadically, or users report frequent timeouts or error messages such as “Too many connections.”
- Difficulty accessing the web: The flood of malicious traffic might consume most of your internet bandwidth, making it hard to access external sites from your internal network.
Unusual traffic patterns
Deviations from your normal traffic baseline should prompt investigation.
- Sudden, unexplained traffic surge: A massive, unexpected spike in web traffic is a red flag. This is especially true if it happens during off-peak hours or from unusual locations.
- Traffic from a single IP address or range: While DDoS is distributed, some attacks originate from a concentrated set of IPs. Sometimes, a disproportionate volume of requests comes from a specific region or country. If you don’t do much business in that region, alarm bells should be ringing.
- Requests to a single endpoint: A sudden, overwhelming number of requests to a specific page, login portal, or API endpoint is a definite anomaly, especially if the asset doesn’t usually receive such concentrated demand.
- Unusual behavioral profiles: A deluge of traffic from users who share a single behavioral profile (e.g. all use the same browser version, device type, or obscure operating system) can indicate bot activity.
Resource exhaustion on servers and devices
Since DDoS attacks aim to exhaust resources, here are the tell-tale signs:
- Spikes in CPU or memory usage: Your servers’ CPU and memory utilization may suddenly skyrocket without any obvious increase in legitimate activity.
- Maxed-out bandwidth: Your internet connection bandwidth may show 100% utilization, strangling normal usage.
- High number of open connections: Your server logs might show a high number of half-open TCP connections (a sign of a SYN flood) or other connection-related errors.
Complaints and external notifications
Sometimes, the first indication comes from your users or providers.
- Customer and employee complaints: Your customers or employees will be quick to notice if your services are slow or if there are issues accessing internal applications.
- Alerts from your ISP or hosting provider: Your Internet Service Provider (ISP) or cloud service provider often has advanced monitoring systems. They should alert you if they detect suspicious patterns targeting your networks.
- Ransom demands: If crippling your services is part a ransomware operation, you’ll likely soon hear from the criminals. They’ll send you direct messages demanding a ransom in exchange for stopping the attack.
Types of DDoS Attacks
DDoS attacks differ in terms of targeting and complexity. While they all broadly focus on exploiting network protocols and server capacities, there are three distinctly defined categories: volumetric attacks, protocol attacks, and application layer attacks.
Volumetric attack
Volume-based attacks flood a target with massive data volumes to consume bandwidth and create digital congestion. Often powered by botnets, they may use amplification techniques to intensify the assault.
Volume overload is the most common and established denial-of-service attack. Examples of this type are:
- UDP flood: The attacker sends a large number of UDP (User Datagram Protocol) packets to random ports on the target. The target server tries to respond to these requests, exhausting its resources.Here are popular use cases:
- ICMP flood: Similar to a UDP flood, this technique uses ICMP (Internet Control Message Protocol) echo requests. The target tries to reply to every incoming request, consuming bandwidth.
- HTTP flood: Bots repeatedly send legitimate-looking HTTP GET or POST requests to a web server. While individual requests might seem normal, the accumulated volume overwhelms the server’s processing ability.
- DNS (Domain Name System) amplification: DNS amplification involves sending a small request to one or more open DNS servers from a spoofed IP address (the victim’s address). In response, these servers send a larger amount of data to the target, amplifying the strike.
Protocol attacks
A protocol attack aims to bring down services by over-consuming the resources of network infrastructure, like load balancers and firewalls. These attacks exploit vulnerabilities in network protocol handling (the rules governing data flows and processing across a network). Also known as state-exhaustion attacks, they may simultaneously attempt to drain server resources.
Examples of protocol attacks include:
- SYN flood: This exploits the TCP (Transmission Control Protocol) three-way handshake. The attacker sends SYN (synchronize) requests to initiate a connection but never sends the final ACK (acknowledgment). The target’s server keeps resources waiting for the incomplete connections, eventually maxing out its memory.
- Fragmentation attacks: The attacker sends fragmented IP data packets that the target system struggles to reassemble, consuming CPU and memory. This prevents it from dealing with legitimate traffic.
Application-layer attacks (Layer 7 attacks)
Application-layer assaults are more sophisticated DDoS attacks targeting specific application functions rather than just raw bandwidth or resources.
While volumetric attacks and, to a lesser extent, protocol attacks crash a service with the sheer number of requests, application layer attacks target an edge server that executes a web application.
They strike at the layer where the server processes HTTP requests to serve web pages to users. By zeroing in on specific functions of a website or app (e.g. search boxes, login pages, or shopping carts), they aggressively use up server CPU and memory.
Examples include:
- Complex HTTP GET/POST flood: The attack targets specific URLs or API endpoints that require significant server processing (e.g. database queries, search functions). The bad actor sends a high volume of seemingly legitimate HTTP requests that are cheap to generate but expensive for the server to process. Each request can require multiple internal operations and file loads.
- The effect is similar to thousands of users simultaneously refreshing a resource-heavy page, overloading the server and degrading performance.
- Low-and-slow attacks (e.g. Slowloris): These attacks keep connections open for as long as possible while sending minimal data. Their goal is to tie up server resources without needing a tsunami of traffic.
How Do You Prevent a DDoS Attack?
Seeing as attackers use increasingly sophisticated tactics, detection remains a challenge for many companies, making complete prevention an unrealistic expectation.
Here’s an idea of why detection is so complex:
- The traffic looks legitimate: Because each bot is an actual internet device, separating the attack traffic from legitimate traffic is tricky. Data packets in the flood look just like the regular requests a website receives from real users, making them hard to spot.
- The assault is distributed: Traffic comes from many different sources globally, making simple IP blocking ineffective.
- Tactics evolve: Cybercriminals constantly develop new methods and refine existing ones to bypass defenses.
While there may be no silver bullet defense, a layered defense incorporating the following strategies can significantly reduce risks.
Content Delivery Network (CDN) with DDoS mitigation
A Content Delivery Network (CDN) is a global system of servers that delivers web content to users based on their geographical location. While more widely used to speed up the delivery of images and video through caching, CDNs can also help to prevent DDoS attacks.
When combined with DDoS mitigation features, a CDN is able to absorb and filter abnormal traffic loads before they reach your origin server. By handling high-volume barrages at the network edge, the CDN helps shield core systems from overload while reducing latency (delays in data transmission).
Anomaly detection and behavior analysis
Today, automation and machine learning are effectively deployed to identify and block cyberthreats in real time. Anomaly detection systems continuously monitor traffic patterns and learn what “normal” behavior looks like across your network. When unusual spikes or irregular patterns occur, the system flags the activity as potentially malicious.
By using machine learning algorithms, these tools adapt over time and become better at distinguishing legitimate user traffic from DDoS activity. This enables security teams or an automated system to respond swiftly and act before the attack reaches full impact.
Anomaly detection doesn’t prevent DDoS attacks outright, but it’s a critical part of a proactive, automated strategy that helps safeguard performance and uptime.
Use a web hosting provider with built-in DDoS protection
Instead of hosting your website and systems on your servers, you can use a professional web hosting provider. Choose a provider that includes DDoS protection as part of its service, whether at the infrastructure, network, or application level. For example, services like Amazon’s AWS Shield can absorb massive attack traffic before it ever reaches your server.
How Do You Mitigate a DDoS Attack?
When faced with an unfolding DDoS attack, your priority is to mitigate the disruption and keep your systems available to genuine users.
Here are the mitigation measures you should take:
Network scalability and redundancy
A high-level approach to minimize distributed denial-of-service attacks is to increase your network’s resilience through redundancy and scalability. This strategy is also known as infrastructure hardening.
- Redundancy ensures backup systems or servers are in place to maintain operations if one part of the network crashes. This is achieved by using load balancing to distribute traffic evenly across multiple servers. The idea is to prevent a single point of failure from causing a complete shutdown.
- Scalability ensures your systems can handle sudden, unexpected demand surges. Leveraging cloud-based services with elastic scaling enables you to add resources quickly during an attack. This way, you absorb the malicious efforts and keep your services live.
Anycast routing
Anycast routing uses an Anycast network to spread attack traffic across multiple distributed servers.
Rather than overwhelming a single point, the flood is dispersed widely to lessen its impact, providing greater resilience and reduced strain on any single server. Legitimate users are connected to the nearest healthy or least-congested server within the global network to maintain communications.
Anycast is widely used by Content Delivery Networks (CDNs) and DNS providers as a first line of defence against high-volume attacks.
Rate limiting
Rate limiting controls the number of requests a user or system can make within a given timeframe.
Rate limits can be adjusted dynamically in real time. During a DDoS attack, security teams can tighten the limits to slow requests per user or IP address. For example, the permitted flow might be reduced from 3 requests per second to 1 per second. This process is often automated, using rules to detect threatening patterns and respond accordingly.
Rate limiting can help to quickly throttle the flood without completely locking out legitimate users. However, because it’s based on individual user/IP limits, it’s less effective in mitigating a large-scale distributed attack where connection requests come from thousands of sources.
Blackhole routing and sinkholing
Blackhole routing and sinkholing involve redirecting malicious traffic away from the target system.
Sinkholing redirects the bad traffic to a controlled server (called a “sinkhole”) where it can be analyzed and neutralized. It’s designed to keep your systems available to genuine customers.
Blackhole routing is a blunt force instrument that network administrators are sometimes forced to use. It works by creating a “black hole” route, effectively dropping all the traffic at a router. While quickly stopping the deluge and halting the strike, it achieves the attacker’s goal of denying service. By pushing both legitimate and malicious traffic into the black hole, the network becomes inaccessible to all.
An Internet Service Provider (ISP) might use black hole routing during severe DDoS incidents to prevent wider network damage, but it’s generally considered a last resort.
More nuanced filtering and management methods are favored to selectively block malicious traffic while trying to keep services available.
Advanced traffic filtering
Advanced traffic filtering precisely identifies and blocks only malicious requests during a DDoS attack, keeping legitimate users online. This requires real-time analysis and intelligent rules.
Key techniques here include:
- Geo-blocking: Limits or blocks traffic from specific geographic regions where genuine users are unlikely to be located.
- IP reputation blocking: Filters traffic from known malicious IP addresses using continually updated threat intelligence databases.
- Access Control Lists (ACLs): ACLs involve setting rules on network devices that explicitly allow or deny traffic based on criteria like source IP, destination, or port. These can block known attackers or rate-limit suspicious traffic.
These filtering techniques, especially when combined with real-time traffic analysis and machine learning for anomaly detection, have proven very effective in DDoS defense and mitigation.
Web Application Firewalls (WAF)
A Web Application Firewall monitors and controls HTTP traffic between a web application and the internet. It can detect and block malicious traffic patterns, such as those used in application-layer DDoS attacks like HTTP floods, and is especially effective against low-volume events that mimic legitimate user approaches.
WAFs can be set to differentiate between regular and abnormal behavior, reducing the incidence of false positives (false warnings).
Why choose Acrisure Cyber Services?
For over two decades, Acrisure has built long-term relationships with hundreds of satisfied clients, successfully defending against countless hackers and cybercriminals and earning awards for service excellence along the way.
Our commitment goes beyond immediate protection, as we proactively anticipate future threats by embracing the key trends shaping the security landscape. These include advanced threat intelligence, machine learning, and future-focused cloud solutions.
When you partner with Acrisure Cyber Services, our skilled specialists, armed with cutting-edge toolkits, become part of your team. For extra peace of mind, we also offer industry-leading insurance to cover you in the event of an unpreventable attack.
Besides cybersecurity services, we also offer comprehensive managed IT solutions and co-managed IT services, adding value to your in-house team.
DDoS Protection Solution with Acrisure Cyber Services
Acrisure’s 360° cybersecurity approach places your organization at the center of a high-grade defense structure. Our full-suite cybersecurity solutions include robust multi-layered DDoS protection. We work dedicatedly with all our clients to identify, prevent, and mitigate events that cause fallouts like:
- Business disruption and downtime
- Financial losses
- Reputational damage
- Weakened infrastructure
Our core DDoS protection capabilities include:
- AI-based anomaly detection and prevention: We utilize the latest artificial intelligence and machine learning to monitor network traffic in real time. These advanced tools quickly identify and neutralize behavior that may signal a DDoS attack.
- Network security: Strong network security and performance, backed by advanced firewalls and smart traffic management, to create proactive defense capabilities.
- Vulnerability and risk assessments: We conduct ongoing vulnerability scans, monitoring, and investigations to proactively identify and address weaknesses that could be exploited in a DDoS attack.
- Infrastructure hardening: Our team places a strong focus on building resilience, including cloud server services to support scaling and redundancy.
- Training and guidance: We can train your security teams in DDoS mitigation techniques like traffic filtering, malicious traffic redirection, and more.
FAQs
Can a small business be targeted by a DDoS attack?
Yes, small businesses are increasingly targeted, especially if they lack strong cybersecurity defenses. DDoS attacks can be used for extortion, competition sabotage, or as a diversion for other attacks.
Is DDoS used as part of ransomware attacks?
How often you scan depends on your risk level, system complexity, and compliance needs. If your systems change often or you’re in a high-risk industry, continuous scanning is advisable.
For critical and public-facing systems, scan at least weekly or even daily. For less critical setups, monthly or even quarterly scans may be enough. Some standards, like PCI DSS, require scans every three months. However, following only the bare minimum can expose you to new threats.
Scanning after major system changes is important. You should also scan when dangerous emerging threats (e.g. WannaCry Ransomware) are identified so you can close new security gaps urgently.
How long do DDoS attacks last?
A vulnerability scan is usually a point-in-time assessment using automated tools to detect known security issues and common vulnerabilities. It is a specific type of security scan.
A security scan also checks for security flaws and critical vulnerabilities, but its scope is larger. It employs more tools and techniques. Besides vulnerability scans, it may also check firewall rules and user permissions. It often incorporates network mapping – a visual representation of all the network’s devices, systems, and connections.
Can a VPN stop a DDoS attack?
Vulnerability scanner tools cannot identify vulnerabilities like the following:
- Zero-day vulnerabilities: Newly discovered flaws not yet been recorded in vulnerability databases.
- Advanced attack techniques: Sophisticated methods like well-disguised malicious code can bypass automated scanners.
- Business logic flaws: Scanners lack the contextual understanding needed to identify issues in application workflows or logic. For example, they might not catch multiple fraudulent transactions of $499 because they only know to refer to amounts of $500+.
- Polymorphic malware: Attackers modify existing threats to create variants that evade signature-based detection. Vulnerability scanners battle to keep up.