What is a DDoS Attack? How They Work and How to Stop Them

Have you ever tried to visit a website, only to be met with an error message that the site is unavailable? Chances are, the site may have been targeted by a Distributed Denial of Service (DDoS) attack.

DDoS attacks are a significant threat in today’s digital world, with recent attacks growing in scale, sophistication, and frequency. In this guide, we will demystify DDoS attacks by exploring what they are, who conducts them, why they happen, and most importantly – how you can protect your own website or application.

Even a basic understanding can go a long way towards establishing an effective defensive strategy against the botnet hordes.

What Exactly Is a DDoS Attack?

DDoS attacks attempt to make your website or web application unavailable to legitimate users by overwhelming it with bogus traffic from multiple sources. Using a real world example, think of it like this:

• Your website is a shop with limited staff and registers
• Hundreds of “customers” suddenly flood through the doors
• They overwhelm your employees and point-of-sale systems
• Legitimate shoppers can’t get in to make actual purchases

It’s the same premise with a digital assault on your site or app. The fake visitors essentially clog your bandwidth and resources, crowding out genuine users trying to access your platform. This can lead to lost sales, falling ad revenues, and frustrated site visitors.

Two Main Types of DDoS Attacks

DDoS attacks generally fall into two main categories:

Volume-Based Attacks

As the name suggests, these attempts aim to tie up your bandwidth and resources by hitting your servers with an avalanche of bogus data requests. Common examples include:

• UDP floods – barraging targets with User Datagram Protocol (UDP) packets
• ICMP floods – overwhelming systems with bogus Internet Control Message Protocol (ICMP) traffic
• SYN floods – repeatedly sending synchronization requests to web servers

Application-Layer Attacks

Rather than simply flooding your site with junk traffic, these assaults target vulnerabilities in your web applications and servers. For instance:

• Slowloris attacks – opening multiple connections with your servers and keeping them open as long as possible
• GET/POST attacks – repeatedly sending legitimate-looking GET and POST requests to crash your site
• DNS query floods – overloading Domain Name System (DNS) servers with lookup requests
• SSL renegotiation attacks – repeatedly initiating bogus Secure Sockets Layer (SSL) renegotiations to sap server resources

While volume-based attacks aim for brute force, application-layer assaults attempt to be more surgical by exploiting flaws in your web infrastructure.

Who Launches DDoS Attacks and Why?

You may be wondering why anybody would take the time and effort to target websites with DDoS attacks. In general, you can usually boil it down to three main motivations:

1. Extortion

In many cases, cybercriminals launch DDoS assaults with the goal of extorting money from victims. They essentially hold your website hostage until you pay a hefty “ransom” fee to call off the bogus traffic flood. Of course, this simply encourages perpetrators to attack you again in the future.

2. Competition/Revenge

Groups like the infamous Lizard Squad have claimed responsibility for DDoS attacks against platforms like Xbox Live and the PlayStation Network. Their main motivation seems to be causing as much chaos as possible and demonstrating their technical prowess.  On the other hand, some sites are targeted by competitors or even disgruntled ex-employees that are looking to take some sort of revenge.

3. Hackctivism

The activist group Anonymous often organizes DDoS attacks against sites and organizations it finds objectionable, like banking institutions or government agencies. The perpetrators likely feel these assaults draw attention to perceived social injustices – otherwise known as ‘hacktivism.’ However, the effectiveness and ethics of such tactics are questionable at best.

In some cases, these attacks originate from multiple botnets simultaneously, indicating cybercriminals are renting out their botnets to those willing to pay.

How Are DDoS Assaults Launched?

If one person sitting at one computer tried to take down a major site, they likely wouldn’t get very far. That’s why sustained, large-scale DDoS attacks rely on botnets – networks of compromised internet-connected devices covertly controlled by a hacker. Common examples include:

• Compromised computers – viruses infect PCs and covertly install malware allowing them to be controlled remotely.
• Exploited IoT devices – attackers identify vulnerabilities in things like WiFi routers, security cameras, and digital video recorders (DVRs) which often have weak security.
• Hijacked servers – poorly configured servers in data centers can get hacked to participate in assaults.

Using botnet management software, an attacker can easily command thousands of compromised devices to send a firehose of bogus traffic towards a target simultaneously. This allows sustained assaults that would be impossible to conduct manually.

Why Are DDoS Attacks So Disruptive?

There are several qualities that make DDoS tactics highly disruptive:

• Difficult to distinguish from legitimate traffic – Since the incoming requests often appear valid on the surface, it’s tough for DDoS mitigation solutions to block them without also blocking real users at the same time.
• Targets unpatched weaknesses – Rather than relying solely on brute force, application-layer attacks exploit vulnerabilities in server configurations most admins overlook.
• Launches from millions of locations – Because assaults harness thousands of geographically dispersed bots, blocking IP addresses becomes impractical.
• Intermittent duration – To avoid detection, attackers alternate between bursts and lulls of bogus traffic. This causes more disruption by denying service sporadically.

Now that you understand DDoS attacks comprehensively, let’s talk about how you can protect your online assets and reputation…

6 Ways to Protect Your Site from DDoS Attacks

While completely bulletproof DDoS protection is difficult (or perhaps impossible), implementing safeguards in layers can help mitigate most threats:

• Set up a Web Application Firewall – A web application firewall inspects incoming traffic and guards malicious requests like SQL injections, cross-site scripting attacks, DDoS attacks, and so on. Turn this on as a first layer of defense for an application attack.
• Conduct Vulnerability Scans Periodically – Proactive vulnerability detection for your servers and web applications allows you to patch the weaknesses before the attackers discover and exploit them.
• Rate Limit – Setting caps on such things as connections per IP addresses, requests per session, and file uploads per minute can constrain brute-force attacks.
• Set IP Reputation Filtering – This includes blacklists of IPs and only allows requests from reputable IP ranges, which are constantly updated.
• Use DDoS Mitigation Services – Third-party specialized services divert traffic through scrubbing centers, which filter out bot attacks before they reach your infrastructure.
• Develop Emergency Plans – Document the incident response plans so that everyone knows their role should an attack actually take place. The ability to put mitigations in place quickly will greatly reduce the time of disruption.

Final Word

While DDoS attacks are on the rise, taking a layered defensive approach goes a long way in keeping your site stable and protected from these cyber threats. With precautions in place, you’ll sleep better knowing your business and its website are safe even as the botnets grow ever more powerful.

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