Which of these countermeasures against a SYN flood attack depends on a challenge-and-response mechanism in which the initiating host is required to send a cryptographic hash that matches some expected value of the receiving host?

SYN flood attack

Explanation:

TCP SYN flood  is a type of Distributed Denial of Service (DDoS) attack that exploits part of the normal TCP three-way handshake to consume resources on the targeted server and render it unresponsive.

Essentially, with SYN flood DDoS, the offender sends TCP connection requests faster than the targeted machine can process them, causing network saturation.

When a client and server establish a normal TCP “three-way handshake,” the exchange looks like this:

In a SYN flood attack, the attacker sends repeated SYN packets to every port on the targeted server, often using a fake IP address. The server, unaware of the attack, receives multiple, apparently legitimate requests to establish communication. It responds to each attempt with a SYN-ACK packet from each open port.

The malicious client either does not send the expected ACK, or—if the IP address is spoofed—never receives the SYN-ACK in the first place. Either way, the server under attack will wait for acknowledgement of its SYN-ACK packet for some time.

you can not change you age soon as you signed up. the only way is too delete your account and use another account to sign up and put your correct age.

assuming you are in the home page.

1) go to the upper right hand corner

2) click on your "profile picture"

3) go down to "edit profile"

4) it should be titled as "edit your profile", click on "profile picture"

5) choose a file

6) press "change"

you're profile picture is updated

~