Table of contents
- What is a DDoS attack?
- What are the main objectives of a DDoS cyber attack?
- Types of DDoS attacks
- Defense strategies against DDoS attacks
In today’s increasingly connected world, cyber security is a fundamental priority for businesses and individuals. Among the most common and devastating threats are DDoS (Distributed Denial of Service) attacks that aim to make websites and online services inaccessible. The targets are often web servers.
What is a DDoS attack?
A DDoS (Distributed Denial of Service) attack is a malicious attempt to disrupt the normal traffic of a server, service, or network by overwhelming it with a flood of Internet traffic. DDoS attacks are orchestrated using multiple compromised machines, often part of a botnet, that coordinate to send requests to the target server. This type of attack can saturate the server’s bandwidth or exhaust system resources, making the online service inaccessible to legitimate users.
What are the main objectives of a DDoS cyber attack?
DDoS attacks can have various objectives, including:
- Service disruption
The primary goal of a DDoS attack is to disrupt access to websites or online services. This can cause significant damage to businesses that rely on their website for daily operations, resulting in financial losses and reputational damage.
- Extortion
Some DDoS attacks are motivated by ransom demands. Attackers threaten to launch or continue the attack unless a ransom is paid.
- Diversion
DDoS attacks can be used as a diversion to hide other malicious activities such as data theft or malware installation.
Types of DDoS attacks
DDoS attacks can be classified into different categories, each with specific methods and objectives. Understanding the differences between these types of attacks is crucial for implementing effective defense measures. Below we explore the main types of DDoS attacks:
Volumetric sttacks
- ICMP Flood (Ping Flood)
Uses ICMP (Internet Control Message Protocol) packets to overwhelm the target with echo requests (pings), saturating the network bandwidth.
- UDP Flood
Sends a large number of UDP (User Datagram Protocol) packets to random ports on the target, causing the server to check for applications listening on these ports and exhausting system resources.
- DNS amplification
Exploits public DNS servers to amplify traffic directed at the target by sending DNS requests with the target’s IP address as the return address, resulting in a massive response to the target.
Protocol attacks
- SYN Flood
The attacker sends a series of SYN requests (the start of a TCP connection) to the target. The server responds with a SYN-ACK packet, but the attacker never completes the connection, leaving many open and unusable connections, exhausting available resources.
- ACK Flood
Similar to the SYN Flood, but uses ACK packets to overload the server, particularly effective against security devices that need to analyze each packet.
- Fragmentation attack
Sends fragmented packets to the target, which must be reassembled. The reassembly process consumes significant system resources, slowing down or crashing the server.
Application layer attacks
- HTTP Flood
The attacker sends a large number of HTTP requests to the web server. These requests can appear legitimate but their volume and frequency overload the server, making the website slow or inaccessible.
- Slowloris
Sends incomplete HTTP requests to the server, keeping connections open as long as possible, consuming all available server connections and preventing legitimate user access.
- Application layer attack (layer 7)
Targets specific functionalities of applications, such as sending heavy database queries, causing intensive resource usage on the server.
Multi-vector attacks
- Multi-vector attacks combine several attack techniques to maximize damage. For example, an attack may start with a SYN Flood to exhaust system resources, followed by an HTTP Flood to overload the web application. These attacks are particularly difficult to mitigate as they require a complex and coordinated response.
Defense strategies against DDoS attacks
Defending against DDoS attacks requires a multifaceted approach that integrates advanced technologies, proactive processes, and strategic collaborations. Below we explore key strategies to protect web servers and online services from DDoS attacks:
Network traffic monitoring
- Traffic analysis tools
Use tools like Wireshark, NetFlow, or cloud monitoring tools to analyze traffic flows and identify abnormal patterns.
- Alert systems
Configure alert systems to notify network administrators when traffic spikes or suspicious activities are detected.
- Behavioral analysis
Implement behavioral analysis solutions that learn normal traffic patterns and can detect deviations indicative of an attack.
IP address filtering
- Blacklists
Use regularly updated blacklists to block IP addresses from which malicious traffic originates.
- Whitelists
Create whitelists of trusted IP addresses to ensure legitimate traffic is not blocked during an attack.
- Geo-Blocking
Block traffic from geographical regions from which no legitimate traffic is expected.
Rate limiting
- Rate limiting configuration
Configure servers and firewalls to limit the number of requests per IP address, preventing a single attacker from overloading the server.
- Application layer rate limiting
Implement rate limiting at the web application level to protect specific critical endpoints.
Content Delivery Network (CDN)
- Load distribution
Use a CDN to distribute traffic across multiple servers in different geographical locations, reducing the risk of overload on a single access point.
- Integrated protection
Many CDNs offer integrated DDoS protection that can detect and mitigate attacks before they reach the origin server.
DDoS mitigation services
- Cloudflare
Offers DDoS mitigation solutions to protect websites and applications from volumetric and protocol attacks.
- Akamai
Uses a global network to filter malicious traffic and protect online resources.
- Arbor networks
Provides AI-based and traffic analysis defense solutions against DDoS attacks.
Redundancy and failover
- Load balancing
Use load balancers to distribute traffic among multiple servers, ensuring no single server is overloaded.
- Redundant servers
Configure redundant servers in different geographical locations to ensure service continuity.
- Multiple data centers
Distribute resources across multiple data centers to prevent a single point of failure from compromising the entire service.
Firewalls and Intrusion Prevention Systems (IPS)
- Web Application Firewalls (WAF)
Implement WAFs to protect web applications from application-layer attacks.
- Intrusion Detection and Prevention Systems (IDPS)
Use IDPS to monitor and respond to threats in real-time, blocking suspicious traffic.
Collaboration with Internet Service Providers (ISP) ì
- Service Level Agreements (SLA)
Establish SLAs with ISPs that include DDoS protection measures.
- ISP traffic filtering
Request ISPs to implement traffic filtering measures to block DDoS attacks upstream.
FAQ
- What is a DDoS attack?
A DDoS attack is an attempt to overload a server, service, or network with excessive traffic to make it inaccessible to legitimate users. - What are the main objectives of a DDoS attack?
The main objectives include service disruption, extortion, and diversion to mask other malicious activities. - What types of DDoS attacks exist?
There are volumetric attacks, protocol attacks, and application-layer attacks, each with different methods to overload the target. - How can a server be defended against a DDoS attack?
Defensive strategies include traffic monitoring, IP address filtering, rate limiting, using CDNs, DDoS mitigation services, redundancy and failover implementations. - What is a botnet?
A botnet is a network of compromised computers used to launch coordinated DDoS attacks. - What is the role of internet service providers in defending against DDoS attacks?
ISPs can implement traffic filtering measures and collaborate with clients to mitigate attacks. - Why are DDoS attacks considered major cyber threats?
DDoS attacks can cause significant service disruptions, financial losses, and reputational damage, making them a critical threat to businesses and online services.
