A security device, comprising: one or more processors configured to: receive a request from an attacker device and intended for a server device; identify the request as being associated with a malicious activity, the malicious activity including one or more undesirable tasks directed to the server device; generate a first unsolvable completely automated public Turing test to tell computers and humans apart, CAPTCHA, based on identifying the request as being associated with the malicious activity, wherein the unsolvable CAPTCHA is a test for which any response from the attacker device will not be treated as solving the test, thereby generating a CAPTCHA configured to attempt to block the attacker device without making the attacker device aware that the attacker device is being blocked, the first unsolvable CAPTCHA being generated using at least a first construction technique, and provide the first unsolvable CAPTCHA to the attacker device; receive, from the attacker device, a first solution associated with the first unsolvable CAPTCHA; notify the attacker device that the first solution is incorrect regardless of whether the received first solution is actually correct; generate a second unsolvable CAPTCHA using a second construction technique after notifying the attacker device that the first solution is incorrect, the second construction technique being different from the first construction technique; provide the second unsolvable CAPTCHA to the attacker device; receive a second solution associated with the second unsolvable CAPTCHA; notify the attacker device that the second solution is incorrect regardless of whether the second solution is actually correct; and based on identifying the request as being associated with the malicious activity, not forward the request to the server device. receive a request from an attacker device and intended for a server device; identify the request as being associated with a malicious activity, the malicious activity including one or more undesirable tasks directed to the server device; generate a first unsolvable completely automated public Turing test to tell computers and humans apart, CAPTCHA, based on identifying the request as being associated with the malicious activity, wherein the unsolvable CAPTCHA is a test for which any response from the attacker device will not be treated as solving the test, thereby generating a CAPTCHA configured to attempt to block the attacker device without making the attacker device aware that the attacker device is being blocked, the first unsolvable CAPTCHA being generated using at least a first construction technique, and provide the first unsolvable CAPTCHA to the attacker device; receive, from the attacker device, a first solution associated with the first unsolvable CAPTCHA; notify the attacker device that the first solution is incorrect regardless of whether the received first solution is actually correct; generate a second unsolvable CAPTCHA using a second construction technique after notifying the attacker device that the first solution is incorrect, the second construction technique being different from the first construction technique; provide the second unsolvable CAPTCHA to the attacker device; receive a second solution associated with the second unsolvable CAPTCHA; notify the attacker device that the second solution is incorrect regardless of whether the second solution is actually correct; and based on identifying the request as being associated with the malicious activity, not forward the request to the server device.