Common Network Attacks Explained

A network attack is an attempt to breach, disrupt, or intercept a network or its data without authorization. A network attack targets the confidentiality, integrity, or availability of a network, using methods that range from flooding a server with traffic to intercepting communication between two parties. The Open Worldwide Application Security Project (OWASP) and the National Institute of Standards and Technology (NIST) document these attack types and their defenses.

This article defines a network attack, then explains the major types: distributed denial-of-service, man-in-the-middle, packet sniffing, spoofing, DNS poisoning, port scanning, and brute-force attacks. Each section states how the attack works and how to defend against it. A table summarizes each attack with its method and defense.

Each section connects the attack to the part of the CIA triad it threatens. The result is a complete account of the common network attacks, how each operates, and the controls that defend a network against them.

What Is a Network Attack?

A network attack is an unauthorized attempt to breach, disrupt, or intercept a network or its data, targeting the confidentiality, integrity, or availability of network resources. A network attack exploits a weakness in a device, protocol, or user to reach a goal the attacker is not permitted to achieve. The defining traits of a network attack are listed below:

• Unauthorized intent defines an attack, since the actor lacks permission to access or disrupt the network.
• A target in the CIA triad is always confidentiality, integrity, or availability.
• An exploited weakness lies in a device, a protocol, a configuration, or a user.
• A method ranges from flooding and interception to deception and credential guessing.

A network attack threatens the confidentiality, integrity, or availability that the CIA triad defines, the goals detailed in the overview of network security. Detecting an attack in progress is the role of network monitoring.

What Is a DDoS Attack and How Do You Defend Against It?

A distributed denial-of-service (DDoS) attack floods a target with traffic from many sources to exhaust its resources and block legitimate users, and it is defended by traffic filtering and rate limiting. A DDoS attack targets availability, overwhelming a server or link until it cannot respond. The mechanics and defense are listed below:

• Distributed sources send traffic from many compromised devices, often a botnet, at once.
• Resource exhaustion consumes bandwidth, connections, or processing until service fails.
• Traffic filtering blocks malicious sources at the firewall or a dedicated mitigation service.
• Rate limiting caps requests per source to keep a flood from overwhelming the target.

A DDoS attack targets availability by exhausting resources, and defenses combine firewall filtering, rate limiting, and upstream mitigation services, according to CISA guidance. Distributing traffic across redundant servers also keeps a service reachable during an attack.

What Is a Man-in-the-Middle Attack and How Do You Defend Against It?

A man-in-the-middle attack, also called an on-path attack, secretly intercepts traffic between two parties to read or alter it, and it is defended by encryption and authentication. A man-in-the-middle attack targets confidentiality and integrity, placing the attacker between sender and receiver. The mechanics and defense are listed below:

• Interception positions the attacker on the path between two communicating parties.
• Reading or altering lets the attacker steal data or change it before it reaches the destination.
• Encryption defends by making intercepted traffic unreadable without the key, as in TLS and VPNs.
• Authentication defends by verifying each party’s identity, exposing an impostor in the middle.

A man-in-the-middle attack is defended by encrypting traffic so interception yields no readable data, the protection a VPN provides across untrusted networks. Comparing the tools that route and protect traffic is the subject of the VPN and proxy comparison.

What Is Packet Sniffing and How Do You Defend Against It?

Packet sniffing, also called eavesdropping, captures and reads network traffic in transit, and it is defended by encrypting data so captured packets stay unreadable. A packet sniffing attack targets confidentiality, collecting data that crosses a network the attacker can observe. The mechanics and defense are listed below:

• Traffic capture uses a tool that records packets passing through a network segment.
• Data extraction reads unencrypted contents such as credentials and messages from the captured packets.
• Encryption defends by converting traffic to ciphertext, so captured packets reveal nothing useful.
• Network segmentation defends by limiting the traffic an attacker on one segment can observe.

Packet sniffing targets confidentiality by reading traffic in transit, and encryption is the primary defense, since encrypted packets carry no readable data. Switched networks and segmentation further limit which traffic an attacker can capture from a single point.

What Are Spoofing and DNS Poisoning Attacks?

Spoofing falsifies an address to impersonate a trusted source, and DNS poisoning corrupts domain name records to redirect users to a malicious destination, both defended by authentication and validation. These attacks target integrity, tricking a network or user into trusting false information. The mechanics and defense are listed below:

• IP spoofing forges a source IP address to impersonate a trusted device and bypass filtering.
• ARP spoofing sends false address-resolution replies to link the attacker’s hardware to a victim’s IP.
• DNS spoofing and poisoning insert false records so a domain name resolves to a malicious server.
• Validation defenses include DNSSEC for DNS records, packet filtering for spoofed IPs, and dynamic ARP inspection for ARP.

Spoofing and DNS poisoning target integrity by falsifying addresses and records, and defenses include the Domain Name System Security Extensions (DNSSEC) and ingress filtering, according to IETF and NIST guidance. These deception attacks join the broader set in the overview of network security.

What Are Port Scanning and Brute-Force Attacks?

Port scanning probes a network to find open ports and services, and a brute-force attack tries many credential combinations to gain access, both defended by firewalls, monitoring, and account lockouts. Port scanning is reconnaissance, while brute force is an access attempt. The mechanics and defense are listed below:

• Port scanning sends probes to a range of ports to map which services a target runs.
• Brute-force attack submits many password or key guesses until one succeeds.
• Firewall filtering defends by closing unused ports and limiting which services are reachable.
• Account lockout and rate limiting defend brute force by blocking after repeated failed attempts.

Port scanning maps a target before an attack, while a brute-force attack guesses credentials to gain entry, and both are defended by firewalls, monitoring, and lockout policies. A firewall that closes unused ports limits scanning, the function detailed in the analysis of hardware and software firewalls.

Common Network Attacks Comparison Table

How Do You Defend a Network Against Attacks?

A network is defended against attacks by combining encryption, firewalls, segmentation, monitoring, and access control into a layered defense. A single control does not stop every attack, so a secure network stacks controls that each address different attack types. The core defenses are listed below:

• Encryption defends interception attacks by making captured traffic unreadable.
• Firewalls defend by filtering traffic and closing ports that scanning and intrusion target.
• Segmentation defends by limiting how far an attacker spreads after a breach.
• Monitoring defends by detecting attacks in progress so a response can follow.
• Access control defends by limiting credentials and permissions that brute force and theft target.

Layering encryption, firewalls, segmentation, monitoring, and access control defends a network against the full range of attacks, the defense-in-depth approach in the overview of network security. Continuous observation of traffic for attack signatures is the role of network monitoring.

What Is a Botnet in Network Attacks?

A botnet is a network of compromised devices controlled remotely by an attacker and used to carry out large-scale attacks such as distributed denial-of-service. A botnet turns infected computers, servers, and connected devices into a coordinated tool the operator commands. The traits of a botnet are listed below:

• Compromised devices are infected by malware that places them under the attacker’s control without the owner’s knowledge.
• Command and control lets the operator direct every infected device from a central point.
• Coordinated attacks use the combined devices to flood targets, send spam, or spread malware.
• Scale gives a botnet the traffic volume that makes a distributed denial-of-service attack effective.

A botnet supplies the distributed sources behind a DDoS attack, multiplying the traffic a single device could not produce alone. Defending against botnet recruitment relies on the malware protections and access control in the computer security basics, while detecting botnet traffic uses network monitoring.

Key Takeaways

• A network attack is an unauthorized attempt to breach, disrupt, or intercept a network.
• A DDoS attack floods a target to exhaust resources, defended by filtering and rate limiting.
• A man-in-the-middle attack intercepts traffic, defended by encryption and authentication.
• Spoofing and DNS poisoning falsify addresses and records, defended by validation and DNSSEC.
• Port scanning and brute force probe and guess, defended by firewalls and lockouts.
• Layered defense combines encryption, firewalls, segmentation, monitoring, and access control.

Last Thoughts on Common Network Attacks

A network attack is an unauthorized attempt to breach, disrupt, or intercept a network, targeting the confidentiality, integrity, or availability of its resources. Distributed denial-of-service attacks exhaust availability, man-in-the-middle and packet sniffing attacks target confidentiality, and spoofing and DNS poisoning attacks corrupt integrity, while port scanning and brute force probe and guess their way toward access.

Each attack has a defense, and layering encryption, firewalls, segmentation, monitoring, and access control provides defense in depth. Readers can continue with the overview of network security, the guide to network monitoring, the analysis of hardware and software firewalls, or the guide to how networks work.