What Is a DDoS Attack and How Do You Defend Against It?

Your website runs fine one minute. The next, it stops responding. Customers see an error page. Your phones light up. Nothing broke on your end, yet nothing works. A distributed denial of service attack floods your servers with fake traffic until real users cannot get through. In 2023, hacktivist groups knocked Government of Canada sites, Senate pages, and airport portals offline this way. The method is cheap, loud, and aimed at any Canadian organization with a public web presence.

A DDoS attack sends more requests to your service than it will handle. The Canadian Centre for Cyber Security defines it as a cyber attack directing a large volume of malicious internet traffic at a target to overwhelm and disable it. Attackers rarely use one machine. They control thousands of infected devices, called a botnet, and point them all at your site at once. Your server treats every request as real. It tries to answer each one. Then it runs out of capacity, and genuine visitors get nothing.

The Three Types You Face

The Cyber Centre groups DDoS attacks into three kinds. Volumetric attacks flood your network with false data requests and drain your bandwidth. DNS amplification and UDP floods fall here. Protocol attacks exploit weaknesses in how data moves, draining the resources of your firewalls and load balancers. A SYN flood works this way. Application layer attacks target a single application and hide inside normal-looking traffic, which makes them hard to spot. An HTTP flood is one example. Each type needs a different defence, so knowing which one hits you shapes your response.

Why Canadian Organizations Are Targets

DDoS attacks hit Canada across every sector. The Cyber Centre reports campaigns against the Government of Canada, provincial and territorial governments, and the financial and transportation sectors. Some attacks chase publicity. A hacktivist group wants a visible outage to make a political point, so it picks a well-known Canadian target and brags about the result. Other attacks hide a second move. While your team fights the flood, a separate intruder slips in through a side door. In November 2025, Canadian agencies issued a joint warning about hostile actors probing critical infrastructure, from power and water to finance and transportation, through preventable weaknesses.

Size gives you no cover. An attacker rents botnet time for the price of a dinner. A small municipality, a regional clinic, or an online retailer makes an easy mark, because each one runs a public service and rarely staffs a full defence team. The outage costs you in lost sales, missed service, and the hours your staff spend firefighting instead of working. For a business running on its website, an afternoon offline turns into real money gone.

How to Defend Against DDoS

Canadian guidance gives you a clear plan. The Cyber Centre’s advice on defending against DDoS attacks tells you to prepare before an attack lands. Start with a risk assessment to find your weak points. Write a DDoS response plan with named roles and a communication chain, so nobody wonders who does what mid-crisis. Build layered defences. A web application firewall filters bad requests. Rate limiting caps how many requests one source sends. Continuous monitoring flags a spike early, while you still have time to act. Many organizations also contract a managed provider to absorb large floods upstream, before the traffic ever reaches their network.

When an attack hits, work the plan. Record the duration, the method, and the assets under fire. Watch for a second wave, because attackers often return. Measure the financial and reputational cost, and tell your customers what happened in plain terms. Afterward, upgrade your defences with the lessons you gathered. This approach fits the Cyber Centre’s Cyber Security Readiness Goals, Canada’s baseline for critical infrastructure operators, and it builds the muscle memory your team needs for the next event.

The Skills Behind Strong Defence

Technology alone will not stop a flood. You need trained people. The work starts at the network layer, where DDoS traffic arrives. The Certified Network Practitioner program builds the networking foundation you need to read traffic patterns and spot an attack in progress. Detection and monitoring come next. The Certified Cybersecurity Analyst track teaches you to watch your network, separate a real spike from an attack, and respond with evidence.

When the flood lands, someone runs the response. The Certified Incident Handling Engineer certification covers containment, coordination, and recovery under pressure. Above the technical work sits ownership. A leader sets the budget for mitigation, approves the response plan, and reports the risk to the board. The Certified Information Systems Security Officer program prepares managers to make those decisions. DDoS attacks will not stop, because they stay cheap and effective. The Canadian organizations training their people now ride out an attack in hours. The rest learn the hard way, with their site dark and their customers gone.