Network security refers to the security tools, tactics, and policies that are used to monitor, prevent, and respond to unauthorized network intrusions while also protecting digital assets such as network traffic. Important Points Network Security TechniqueImplementation TechniqueSymmetric encryption is a type of encryption in which the same key is used to encrypt and decrypt data. Both the sender and the recipient have identical copies of the key that they keep private and do not share with anyone. Secret key The implementation techniques of Network security techniques are with the Secret key tool. Asymmetric encryption is a cryptographic algorithm. To generate a key pair, this algorithm employs a key generation protocol (a type of mathematical function). Both keys are mathematically linked to one another. The relationship between the keys varies depending on the algorithm. The algorithm is essentially a combination of two functions encryption and decryption. The public and private keyAsymmetric encryption uses two keys €” a public key (that anyone can access) to encrypt information and a private key to decrypt information. Authentication is the process of identifying users who request access to a system, network, or device. Access control often determines user identity according to credentials like username and password. Other authentication technologies like biometrics and authentication apps are also used to authenticate user identity. Digital signatures function similarly to electronic "fingerprints. "The digital signature, which takes the form of a coded message, securely associates a signer with a document in a recorded transaction. To provide the highest levels of security and universal acceptance, digital signatures use a standard, accepted format known as Public Key Infrastructure (PKI). They are an electronic signature implementation of a specific signature technology (eSignature). A denial of service (DoS) attack is a cyber-attack on a single computer or website with the goal of denying services to intended users. Their goal is to disrupt an organization's network operations by denying users access. Email filterA DoS attack can be prevented by filtering emails from malicious attackers and IP addresses. Additional InformationNetwork security is the defense that is used to protect against ever-increasing cybercrime. Network security encompasses both hardware and software technologies and is intended to respond to a wide range of potential threats to your network. Therefore, the correct answer is A - III, B - I, C - II, D - IV