Building a defense against DDoS attacks

One Against All

Article from ADMIN 79/2024

By Markus Stubbig

Targeted attacks such as distributed denial of service, with thousands of computers attacking your servers until one of them caves in, cannot be prevented, but they can be effectively mitigated.

Cyberattacks come in many forms, such as secret spying on company networks, sabotage, and disruptive actions. In a disruptive action, denial of service (DoS), the attacker attempts to overload a server with requests until it stops working. This attack is easier said than done, because servers usually have more power in reserve than a single client can call up. The obvious idea is to attack the same server with many clients. The resulting attack is called a distributed denial of service (DDoS). The attacker rounds up a huge number of computers in the form of a botnet.

You are not powerless against DDoS attacks, but it is important to introduce appropriate measures up front, because during such an attack, the Internet line is flattened by the flood of client requests and the server farm no longer responds. The simplest, albeit most expensive, measure is to upgrade your infrastructure with more servers and more bandwidth. If your budget allows for this approach, you need read no further. For everyone else, this article describes various ways of efficiently protecting your infrastructure. The aim is not to provide protection against huge attacks that hit at terabit per second rates, but simply to make your servers more robust. The box "CDN" describes why CDNs and DDoS are often mentioned together.

CDN

Many providers mention DDoS and content delivery networks (CDNs) in the same context. A CDN distributes its servers across as many data centers as possible around the world. The aim is to locate the data closer to the customer so the content is delivered locally and not sent halfway around the world. This method saves provider bandwidth and makes the services more responsive for the customer.

As a positive side effect, the CDN provides protection against DDoS attacks because the attacker has to deal with many instances of the same service. If the attacker manages

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