Users are unable to access a company server. The system logs show that the server is operating slowly because it is receiving a high level of fake requests for service. Which type of attack is occurring?

A Denial of Service (DoS) attack overwhelms a server with fake requests, consuming resources and preventing legitimate users from accessing the service. The key symptom is a server operating slowly under a high volume of malicious requests. Reconnaissance (A) is information gathering, access attacks (B) involve unauthorized entry, while worms (D) and viruses (E) are self-replicating malware.