Do not become a zombie! The danger of botnets

It sounds like the plot from a B movie: an evil network of millions of zombie computers threatens the world. Unfortunately, these kinds of networks really do exist. We call them botnets. Prevent criminals from using your devices for a botnet without you noticing.

The number of botnets is growing. In the second quarter of 2023, there were 8,438 worldwide, according to Spamhaus. Qakbot, the world's largest botnet, was dismantled by an international police effort on 26 August 2023. It had been active since 2008, damaging comapnies and public insititutions for hundreds of millions of euros.  

What is a botnet? 

A botnet is a network of robots, or ‘bots’. If your computer is infected by malware, it can become part of such a bot network. Botnets consist of hundreds, thousands, or even millions of infected ‘zombie’ computers. The manager of the botnet can remotely instruct your computer. A botnet can take over any device if it is connected to the internet.Think of smart refrigerators or televisions. 

Spam and DDoS attacks 

Behind a botnet is a botmaster, who manages the 'zombie army'. The manager uses a botnet to cause all sorts of trouble. For example, they might issue a command such as: send a spam message to this email address, or: launch a DDoS attack on that IP address. Criminals also use botnets for spreading phishing messages and malware. Or for cryptojacking, an illegal type of cryptomining. As we connect more devices to the internet, bot networks can get bigger and stronger. 


If a botnet takes over your devices, your company becomes vulnerable to other cyber attacks. The criminals are inside your network. Suppose criminals take over the camera network you use to secure your business premises. They will be able to see exactly what is going on in and around your company. Or criminals can infect your computer with ransomware. This will lock your computers. Only if you pay a ransom will the criminals unlock your files, so you can get back to work.  

Removing botnets 

It is hard to tell whether your device has been taken over by a bot network. But there are clues, such as a slow internet connection, or strange emails your contacts tell you they have been getting from you. Sometimes your internet provider warns you that a bot network has taken over your device. Another good tip-off can come from your antivirus programme. It can often prevent malware infection. Or remove malware, so that your device is no longer part of a botnet. The police also regularly take botnets offline. You can check (in Dutch) if your devices are among them. 

Do not become a zombie 

How do you prevent a botnet from turning your device into a zombie?  

  • Stay alert: are you buying a device that you can connect to the internet? Pay close attention to security. Always change default passwords

  • Protect yourself: always run the updates of the software you use. This fixes the vulnerabilities and gives malware less of a chance. 

  • Check what you click on: do not click on dubious links, and never use illegal software, which allows malware in very easily. 

Finally: have you been taken over by a bot network after all? Reset your device, or have an antivirus programme remove the malware. Also change all your passwords, because the botnet may have stolen your data.