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What causes a site to go down

Posted 04th October, 2018

There are countless reasons a site may go down, or be slow to respond. The most common causes are as follows:

  • DDOS attacks
  • Bad hosting
  • DNS issues
  • Malicious code
  • Software failure
  • Bad maintenance

DDOS attacks

Distributed denial of service, or DDOS for short is an automated attack created with the intention of disrupting the normal traffic to a server. This is usually done by “jamming” the traffic to a certain server and in this way disrupting/denying the access to normal users.

While there are multiple types of DDOS attacks, the most common that can be experienced in the application layer (as per the OSI model) are usually connected to making HTTP requests. In simple words this is similar to you refreshing your browser to request your index file, however instead of you imagine millions of bots doing this automatically until a certain resource limit is met and the server goes down and all the sites on that server go down with it.

There are ways to prevent this downtime, however it really depends on the hosting environment you are using at the moment.

Server Errors or Overloading

Hosting issues can range from broken servers, to vulnerable servers, to wider network problems. Even if your host guarantees 99.9% uptime, that's still around a whole day of expected downtime per year.

Often, a server is just overloaded, or one user is causing issues for the others. However, spikes and performance issues can be intermittent or difficult to diagnose.

DNS issues

DNS is a complex art. Changing hosts may also cause disruption due to caching, or a simple DNS typo might cause the whole DNS zone to fail.

Malicious code

No matter what CMS you are using there can always be a risk from malware. Malicious code can come in all forms and affect your website, sometimes from automated attacks and sometimes direct. Hacked sites might still appear online, or might show an error.

Software failure

A software failure can be a component failure (for instance a plugin/extension/module) or a framework failure (such as the core software). This problem is usually preventing by keeping software up to date, and can be fixed by doing the same.

Human Error

Human error, or the lack of human intervention (updates, plugins, maintenance) can cause different problems from software failures to malicious code to the complete deletion of something that should not have been deleted!