The correct answer is 'Brute force attack'. This type of activity suggests an attempt to guess the password by systematically trying numerous possible combinations. A brute force attack often generates many failed login attempts in a short time frame, which would be recorded by an IDS. An IDS is designed to detect this kind of anomalous behavior and raise alerts accordingly. 'Port scanning' involves probing a server for open ports and does not necessarily result in multiple failed login attempts and would not typically generate an IDS alert for this behavior. 'DDoS attack' and 'Phishing attempt' are also incorrect because although they are security threats, they generally do not result in repeated failed logins on a server.