Module Practice and Quiz


What did I learn in this module?

Network security breaches can disrupt e-commerce, cause the loss of business data, threaten people’s privacy, and compromise the integrity of information. Assets must be identified and protected. Vulnerabilities must be addressed before they become a threat and are exploited. Mitigation techniques are required before, during, and after an attack. An attack vector is a path by which a threat actor can gain access to a server, host, or network. Attack vectors originate from inside or outside the corporate network.

The term ‘threat actor’ includes hackers and any device, person, group, or nation state that is, intentionally or unintentionally, the source of an attack. There are “White Hat”, “Gray Hat”, and “Black Hat” hackers. Cyber criminals operate in an underground economy where they buy, sell, and trade attack toolkits, zero day exploit code, botnet services, banking Trojans, keyloggers, and more. Hacktivists tend to rely on fairly basic, freely available tools. State-sponsored hackers create advanced, customized attack code, often using previously undiscovered software vulnerabilities called zero-day vulnerabilities.

Attack tools have become more sophisticated and highly automated. These new tools require less technical knowledge to implement. Ethical hacking involves many different types of tools used to test the network and keep its data secure. To validate the security of a network and its systems, many network penetration testing tools have been developed. Common types of attacks are: eavesdropping, data modification, IP address spoofing, password-based, denial-of-service, man-in-the-middle, compromised-key, and sniffer.

The three most common types of malware are worms, viruses, and Trojan horses. A worm executes arbitrary code and installs copies of itself in the memory of the infected computer. A virus executes a specific unwanted, and often harmful, function on a computer. A Trojan horse is non-self-replicating. When an infected application or file is downloaded and opened, the Trojan horse can attack the end device from within. Other types of malware are: adware, ransomware, rootkit, and spyware.

Networks are susceptible to the following types of attacks: reconnaissance, access, and DoS. Threat actors use reconnaissance (or recon) attacks to do unauthorized discovery and mapping of systems, services, or vulnerabilities. Access attacks exploit known vulnerabilities in authentication services, FTP services, and web services. Types of access attacks are: password, spoofing, trust exploitations, port redirections, man-in-the-middle, and buffer overflow. Social engineering is an access attack that attempts to manipulate individuals into performing actions or divulging confidential information. DoS and DDoS are attacks that create some sort of interruption of network services to users, devices, or applications.

Threat actors can send packets using a spoofed source IP address. Threat actors can also tamper with the other fields in the IP header to carry out their attacks. IP attack techniques include: ICMP, amplification and reflection, address spoofing, MITM, and session hijacking. Threat actors use ICMP for reconnaissance and scanning attacks. They launch information-gathering attacks to map out a network topology, discover which hosts are active (reachable), identify the host operating system (OS fingerprinting), and determine the state of a firewall. Threat actors often use amplification and reflection techniques to create DoS attacks.

TCP segment information appears immediately after the IP header. TCP provides reliable delivery, flow control, and stateful communication. TCP attacks include: TCPSYN Flood attack, TCP reset attack, and TCP Session hijacking. UDP is commonly used by DNS, TFTP, NFS, and SNMP. It is also used with real-time applications such as media streaming or VoIP. UDP is not protected by encryption. UDP Flood attacks send a flood of UDP packets, often from a spoofed host, to a server on the subnet. The result is very similar to a DoS attack.

Any client can send an unsolicited ARP Reply called a “gratuitous ARP.” This mean that any host can claim to be the owner of any IP or MAC. A threat actor can poison the ARP cache of devices on the local network, creating an MITM attack to redirect traffic. ARP cache poisoning can be used to launch various man-in-the-middle attacks. DNS attacks include: open resolver attacks, stealth attacks, domain shadowing attacks, and tunneling attacks. To stop DNS tunneling, the network administrator must use a filter that inspects DNS traffic. A DHCP spoofing attack occurs when a rogue DHCP server is connected to the network and provides false IP configuration parameters to legitimate clients.

Most organizations follow the CIA information security triad: confidentiality, integrity, and availability. To ensure secure communications across both public and private networks, you must secure devices including routers, switches, servers, and hosts. This is known as defense-in-depth. A firewall is a system, or group of systems, that enforces an access control policy between networks. To defend against fast-moving and evolving attacks, you may need an intrusion detection systems (IDS), or the more scalable intrusion prevention systems (IPS).

The four elements of secure communications are data integrity, origin authentication, data confidentiality, and data non-repudiation. Hash functions guarantee that message data has not changed accidentally or intentionally. Three well-known hash functions are MD5 with 128-bit digest, SHA hashing algorithm, and SHA-2. To add authentication to integrity assurance, use a keyed-hash message authentication code (HMAC). HMAC is calculated using any cryptographic algorithm that combines a cryptographic hash function with a secret key. Symmetric encryption algorithms using DES, 3DES, AES, SEAL, and RC are based on the premise that each communicating party knows the pre-shared key. Data confidentiality can also be ensured using asymmetric algorithms, including Rivest, Shamir, and Adleman (RSA) and the public key infrastructure (PKI). Diffie-Hellman (DH) is an asymmetric mathematical algorithm where two computers generate an identical shared secret key without having communicated before.

3.11.3 Module Quiz – Network Security Concepts