What is a botnet?#
The word combines "robot" and "network". When malware is installed on a device and puts it under the command of a remote control server, that device is called a "bot" or "zombie". Thousands or even millions of infected devices together form a botnet, and its operator can use them all at the same time.
An analogy#
Imagine someone secretly holding spare keys to thousands of homes and using their electricity and phone lines whenever they like. The owners usually do not notice, because daily life goes on almost as normal.
What are botnets used for?#
- DDoS attacks that take websites offline
- Sending mass spam and phishing emails
- Trying passwords on login pages (brute-force attacks)
- Fake ad clicks and fake views or followers
- Secretly mining cryptocurrency with the victim's resources
Which devices are at risk?#
Besides computers and phones, Internet of Things devices such as security cameras, modems and routers are popular targets, because they often run with default passwords and are rarely updated.
How to protect your devices#
- Change the default passwords of modems, routers and cameras
- Keep operating systems and device firmware up to date
- Install software only from trusted sources
- Take unexplained slowness, overheating or strange internet usage seriously and scan with antivirus software
Website owners can also reduce botnet traffic with a firewall, CAPTCHA and limits on login attempts.