Distributed Denial of Service (DDoS) attacks are a serious threat facing organizations of all types and sizes. By flooding networks and servers with traffic, DDoS attacks can severely degrade performance and availability of websites and applications.
In this comprehensive guide, we will explore 10 of the most common DDoS attack types, examine in-depth how they work, and provide expert advice on prevention and mitigation strategies.
What is a DDoS Attack?
A DDoS attack seeks to make an online service or website unavailable by overwhelming it with traffic from multiple sources. They work by leveraging botnets – networks of compromised computers and devices that can be coordinated to flood victims with junk requests.
The motives behind DDoS attacks include:
- Disrupting communications and services
- Damaging brand reputation
- Gaining a competitive advantage
- Distracting security teams
Some of the most frequent DDoS targets include:
- Online retailers
- Financial services
- Gaming/gambling
- Government entities
- IT providers
By consuming available bandwidth and overloading infrastructure, DDoS-ers can inflict serious damage like abandoned shopping carts, loss of sales, user frustration, and more.
How Does a DDoS Attack Happen?
DDoS attackers use botnets of infected devices to carry out attacks. By compromising vulnerable routers, IoT gadgets, and mobile devices with malware, attackers can control them remotely as a unified botnet army.
From there, overwhelm tactics involve having each bot flood the target‘s IP address or domain name system (DNS) servers with requests. This sudden deluge of traffic from potentially millions of sources can crash systems and websites.
Major Types of DDoS Attacks
There are three primary categories of DDoS attacks:
1. Application Layer Attacks – Target web server resources by spamming applications with sustained HTTP requests to consume maximum bandwidth. HTTP flooding is most common.
2. Volumetric Attacks – Seek to flood networks and bandwidth availability. Tactics like DNS amplification attacks are used to congest pipes.
3. Protocol Attacks – Exploit inherent weaknesses in networking protocol handshakes and interactions. SYN floods which don‘t properly complete TCP handshakes are an example.
Now let‘s explore 10 specific DDoS attack types in more detail:
1. HTTP Flood
HTTP flood attacks submerge web servers with a tidal wave of HTTP requests from botnets. Servers attempt to process this high volume which consumes resources and renders them unable to respond to legitimate traffic.
Prevention Tips:
- Utilize a CDN and caching to reduce strain on origin servers
- Enable rate limiting in application logic
- Deploy a WAF to filter malicious bot traffic
2. DNS Flood
DNS flood attacks target the domain name system servers that translate human-readable web addresses into machine IP addresses. By overwhelming DNS infrastructure with lookup requests, websites become unreachable.
Prevention Tips:
- Oversizing DNS capacity to handle spikes
- Using a managed DNS provider like AWS Route 53 or Cloudflare
- Configuring anycast routing
3. Ping Flood
Ping flood attacks leverage weaknesses in the ICMP protocol to overwhelm victims with echoed ping requests and replies. This consumes available processing power rendering networks inaccessible.
Prevention Tips:
- Implementing ICMP rate limiting on routers and firewalls
- Blocking ICMP on servers where possible
- Filtering ICMP ingress traffic
4. SYN Flood
SYN floods exploit the TCP three-way handshake by sending successive SYN packets to consume server socket resources used to establish connections. This leaves no room for legitimate users.
Prevention Tips:
- Reducing TCP timeout durations
- Increasing socket availability
- Deploying SYN cookies
5. UDP Flood
Rather than establish proper connections, UDP flood attacks overwhelm victims by transmitting sustained User Datagram Protocol (UDP) traffic. This can crash network infrastructure components.
Prevention Tips:
- Configuring UDP rate limiting
- Applying specialized UDP DDoS mitigation
- Filtering UDP traffic
6. DNS Amplification
DNS amplification attacks abuse public DNS servers to overwhelm victims with drastically amplified attack traffic. Using botnets, attackers fake the victim‘s IP address to harvest excess responses.
Prevention Tips:
- Disabling open DNS resolvers
- Implementing ingress filtering
- Using DNSSEC protocol
7. XML-RPC Pingback
WordPress XML-RPC pingback functionality allows sites to communicate when linking to one another. Attackers abuse this feature to overwhelm targets by initiating excessive pingbacks from botnet sites.
Prevention Tips:
- Disabling XML-RPC in WordPress
- Limiting pingbacks via
xmlrpc.php - Blocking bogus WordPress traffic with mod_security
8. Slowloris
Slowloris utilizes partial HTTP requests from multiple sockets to hog server resources. By slowly dripping traffic, single machines can tie up all available connections and deny access.
Prevention Tips:
- Increasing timeout duration
- Reducing max clients settings
- Load balancing to absorb partial connections
9. Smurf Attack
Smurf attacks spoof victims‘ IP addresses and broadcast large ICMP packets to amplifier networks. This elicits a flood of responses to overwhelm victims resources through sheer traffic volume.
Prevention Tips:
- Disabling ICMP on amplifiers/servers
- Configuring infrastructure to prevent packets sent to broadcast network ranges
- Spoofing and traffic anomaly detection
10. Zero-Day DDoS
Zero-day DDoS attacks target undisclosed vulnerabilities security teams are unaware of and unable to patch. Attackers test new infection methods and exploits using victims as guinea pigs.
Prevention Tips:
- Penetration testing and red teams to identify flaws
- Keeping software updated
- Intrusion detection and analysis to spot anomalies
Conclusions on Preventing DDoS Attacks
As observed, DDoS attackers have diverse tactics available for disrupting online services and websites. The keys to reducing risk include:
Monitoring and Analytics – Spotting attack patterns early is crucial. Use network analytics to establish baselines and alert on anomalies.
Filtering and Rate Limiting – Reduce attack surface by blocking bogus traffic, enabling caching, and limiting requests.
Overprovisioning – Absorb extra capacity by oversizing infrastructure components and enabling auto-scaling.
Anycast Routing – Minimize localized outages by distributing traffic geographically across multiple points of presence.
Expert Managed Solutions – Leverage purpose-built expertise and capacity from vendors offering DDoS protection.
With vigilance, planning, and appropriate safeguards, organizations can manage DDoS risks and maintain website availability during attacks. Expert solutions provide an added layer of protection and peace of mind.
