The acronym 'DDoS' stands for Distributed Denial of Service. It is a significant threat to online services as it involves overwhelming a target with an excessive amount of traffic from multiple compromised sources. This flood of traffic can render the target's systems unable to respond to legitimate user requests, effectively denying service to users and disrupting normal operations. DDoS attacks can be politically motivated, financially driven, or simply intended to cause chaos. Their increasing sophistication has made them a prevalent concern in cybersecurity, requiring proactive measures to mitigate risk.