A server can suffer a DDoS (Distributed Denial of Service) attack even if it is not in active use for several reasons:
Static IP Address: Even if the server is not in use, if it has a static IP address, it remains registered on the internet. Attackers can target this IP address, believing it to be part of a network or service they wish to disrupt.
Past Services: If the server previously hosted services or applications that have since been decommissioned but the server's configuration or DNS records have not been fully updated, it can still be targeted by attackers who are aware of its past use.
Network Location: Servers located in strategic positions within internet infrastructure, such as peering points or near major internet exchanges, might be targeted more frequently as part of broader attacks on these key locations.
Misconfiguration: Improperly configured firewalls, routers, or network services can leave the server vulnerable to DDoS attacks. For example, open ports that are not in use can still be exploited.
Shared Hosting: In shared hosting environments, an attack on one site can inadvertently affect others on the same server, even if those other sites are not actively being used.
Vulnerabilities in Dependencies: Even if the main application is not running, dependencies like databases, web servers, or other services might still be active and vulnerable to attacks.
Example: A company decommissions a web server but fails to properly remove its DNS records. Attackers notice the server's IP address is still resolving to a domain name and use it to launch a DDoS attack, overwhelming the server's network resources.
To mitigate such risks, it's crucial to properly decommission servers by removing them from DNS, updating firewall rules, and ensuring all services are stopped and dependencies are secured. Utilizing cloud services like Tencent Cloud can also provide additional layers of security and DDoS protection through their robust infrastructure and security features.