How a botnet works
An attacker infects devices through phishing, malicious downloads, or by exploiting weak or default passwords and unpatched software. Each infected device, or bot, then connects to a command-and-control (C2) server or a peer network to receive instructions.
The owner of the device usually notices nothing. The operator can direct thousands of bots at once to flood a website, send spam, or run credential-stuffing attempts. Internet of Things devices such as cameras and routers are common recruits because they are rarely patched or monitored.
Why it matters for Canadian organizations
A botnet can hit an organization in two ways: as a target of attacks that originate from one, or as an unwilling host if its own devices are compromised. Both carry costs, from website downtime to damaged reputation and blocklisted email domains.
The Canadian Centre for Cyber Security warns about botnet activity and insecure connected devices. If compromised systems also leak personal information, PIPEDA or Law 25 obligations may be triggered. Unexplained outbound traffic from internal devices is often the first sign that you are part of one.
How to defend against it
Keep operating systems, firmware, and applications patched, and change default credentials on every device, especially routers and IoT equipment. Segment IoT and operational technology from core networks so a compromised camera cannot reach servers.
Monitor outbound traffic and DNS requests for connections to known command-and-control infrastructure, and use endpoint protection. DNS filtering and egress controls can cut bots off from their operators. For availability, DDoS mitigation services help absorb floods from other people's botnets. Replace end-of-life equipment that no longer receives security updates.
Frequently asked questions
What is a botnet used for?
Botnets are used for distributed denial-of-service attacks, sending spam and phishing emails, credential stuffing, spreading further malware, mining cryptocurrency without consent, and sometimes renting out access to other criminals as a service. Many botnets also rent their capacity to other criminals, increasing how widely they are abused.
How do I know if my device is part of a botnet?
Signs include unexplained slowness, high network use when idle, unfamiliar processes, and connections to suspicious addresses. Network monitoring and endpoint detection are more reliable than user observation, because bots are designed to stay hidden. If you suspect infection, isolate the device and involve your security team promptly.
Is a botnet the same as a DDoS attack?
No. A botnet is the infrastructure of compromised machines, while a DDoS attack is one thing attackers use it for. The same botnet can also send spam or steal data, so the two terms are related but different.
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