What is a DDoS attack?
A DDoS attack, or Distributed Denial of Service attack, is a type of cyber attack where multiple compromised devices are used to target a single system and overwhelm it with traffic. This prevents legitimate users from being able to access the system. DDoS attacks work by flooding the target with more requests than it can handle, overloading the server’s resources and causing it to crash or become inaccessible.
Some common features of DDoS attacks include:
- Using botnets – networks of compromised devices infected with malware that allow the attacker to control them
- Exploiting vulnerabilities in poorly secured devices like routers, cameras, etc to make them part of the botnet
- Generating huge volumes of requests from multiple sources to overwhelm the target’s bandwidth
- Overloading state tables, sockets or CPU load on application servers by sending partial requests
- Amplification attacks that abuse protocols to reflect and amplify traffic sent to the victim
The impact of a successful DDoS attack can include website downtime, loss of service, lost revenue, and damage to an organization’s reputation.
What are common DDoS attack vectors?
There are several common vectors that attackers use to conduct DDoS attacks:
Volume-Based Attacks
These attacks aim to flood the network bandwidth of the target system using massive amounts of bogus traffic. Strategies include:
- UDP floods – Leveraging User Datagram Protocol (UDP) by sending high volumes of UDP packets to random ports
- ICMP floods – Exploiting Internet Control Message Protocol (ICMP) with ping floods
- SYN floods – Opening excessive TCP connections by initiating many TCP SYN requests but not responding to the SYN-ACK replies
- HTTP floods – Barraging HTTP requests using a botnet to consume available connections
Protocol Attacks
Protocol attacks consume actual server resources or those of intermediate communication equipment by exploiting vulnerabilities in various protocol implementations. Tactics include:
- DNS amplification – Manipulating public DNS servers to flood targets with huge responses
- NTP amplification – Abusing Network Time Protocol (NTP) servers by spoofing the IP of the target to receive amplified traffic
- SSDP amplification – Exploiting the Simple Service Discovery Protocol (SSDP)
- Chargen amplification – Abusing character generator (CHARGEN) services running on UDP port 19
Application Layer Attacks
These target web server resources and vulnerabilities by disrupting the layer 7 communication between end users and application servers. Examples include:
- Low and slow attacks – Using a small number of connections opened very slowly to avoid detection but collectively consume resources
- HTTP request smuggling – Manipulating how HTTP requests are handled to consume resources
- SSL renegotiation – Initiating Secure Socket Layer (SSL) renegotiations to overload SSL servers
- Application attacks – Targeting specific applications like DNS and SIP servers
Multi-Vector Attacks
Sophisticated DDoS activities often combine multiple vectors mentioned above as layered attacks that are challenging to fully mitigate.
What are the motives behind DDoS attacks?
There can be various motivations for carrying out a DDoS attack:
- Financial gain – Ransom demands for stopping an attack or removing threats of future attacks
- Revenge – Disgruntled customers or former employees attacking a business out of spite
- Hacktivism – Attacks driven by political or social agendas and activism
- Cyber warfare – State-sponsored attacks against strategic targets or political foes
- Distraction – Drawing attention or resources away from other criminal activities happening simultaneously
- Malicious competition – Taking down business rivals
Underground DDoS services have also emerged to provide easy access to stresser tools, botnets for hire, and DDoS infrastructure. The low barriers make it simple for anyone to rent DDoS firepower.
What are common DDoS attack tools?
Attackers leverage a range of tools and technologies to conduct DDoS attacks. Some examples include:
- Botnets – Networks of compromised devices infected with malware allowing remote control by an attacker
- Stressers/Booters – DDoS-for-hire services providing easy access to attack resources
- DDoS bots – Malware programs designed specifically to carry out DDoS floods
- Exploit scripts – Scripts that target vulnerabilities in systems to conscript them into botnets
- Packet crafting tools – Used to create customized malicious packets difficult to defend against
- Spoofing tools – Allows concealing the source of attacks by forging IP addresses
As DDoS tactics and infrastructure become more sophisticated, the bar continues to lower for executing highly disruptive attacks.
What are common DDoS attack targets?
DDoS attacks target organizations across every industry and sector. Some of the most common targets include:
- E-commerce sites – Online businesses are highly vulnerable, especially during peak sales seasons
- Banks and financial institutions – Attacks aim to disrupt time sensitive transactions and access to funds
- Government institutions – High profile public sector entities are attractive targets
- Gaming services – Gaming platforms and supporting infrastructure are impacted by DDoS activities
- Media and entertainment sites – Large amounts of traffic make these sites prone to availability issues
- Cloud service providers – Attacks targeting public cloud networks can affect many customers simultaneously
Attackers may also leverage DDoS techniques as a diversionary tactic while targeting specific organizations for data theft or to overwhelm incident response resources.
What are the business impacts of DDoS attacks?
DDoS attacks can severely impact an organization’s business operations and continuity. Consequences include:
- Website downtime – Unavailability of public-facing online services like e-commerce can lead to major revenue loss
- Loss of productivity – Employees being unable to access needed systems or work during an attack
- Negative customer experiences – Users receiving slow loading times or error messages during peak traffic times
- Damage to reputation – Appearing unable to defend infrastructure against cyber attacks
- Legal and regulatory non-compliance – Potential penalties or obligations if service levels are impacted
- Operational costs – Expenses related to emergency response, outfitting defenses, and implementing solutions
Organizations in every industry are at risk of dealing with these business disruptions.
How can you defend against DDoS attacks?
A robust defense strategy should include a layered approach with the following elements:
Network Traffic Monitoring
Monitor network traffic for abnormal volumes or connections that may indicate DDoS activity. Leverage whitelisting of known legitimate IP addresses. Analyze traffic patterns using baselining to identify anomalies.
Access Control Lists
Implement ACLs (Access Control Lists) to block traffic from suspicious or unused IP address ranges. Keep ACLs updated with current threat intelligence on botnet addresses.
Overprovision Bandwidth
Proactively scale bandwidth to handle sudden spikes in traffic. Work with ISPs to determine optimal bandwidth sizing and have escalation plans for expanding capacity quickly during attacks.
Rate Limiting
Enable rate limiting on external facing systems to throttle excessive connection attempts or requests from a single IP address. This prevents application overload.
Filter Unused Protocols
Disable unused protocols and services that could be exploited to amplify attacks. Close unnecessary ports vulnerable to floods.
Load Balancing
Distribute incoming traffic across multiple servers to increase overall capacity to handle high volumes. Implement load shedding to cut off malicious traffic.
CDN Caching
Leverage content delivery network (CDN) caching and web caching proxies to absorb and filter attack traffic closer to the edge before reaching origin servers.
Null Routing
Redirect traffic from known attack sources to null routes that drop them before resource consumption. This blackholing technique is used by many ISPs.
DDoS Mitigation Services
Use DDoS mitigation services that scrub traffic through massive global scrubbing centers and absorb attacks before they reach the organization.
| Defense Layer | Mechanisms |
|---|---|
| Network Monitoring | Traffic analysis, baselining, whitelisting |
| Access Control | ACLs, address blacklisting |
| Bandwidth Scaling | Overprovisioning, traffic load balancing |
| Request Filtering | Rate limiting, protocol filtering |
| Caching and Offloading | CDNs, web caches, scrubbing centers |
| Traffic Dropping | Null routing, blackholing |
How can you recover quickly from a DDoS attack?
The key steps to swiftly respond and recover after a DDoS attack include:
Continuously Validate Normal Operations
Constantly verify all systems and services are performing as expected without resource constraints or bottlenecks after an attack subsides. Watch for surges in traffic or subsequent attacks.
Conduct Post-Attack Forensics
Analyze traffic during the attack period to understand vectors leveraged and vulnerabilities that may need addressing. Identify gaps that allowed the attack to be successful.
Keep Communications Open
Frequently update internal teams, executives, customers, and partners throughout the attack timeline. Prompt communication reduces speculation and frustration.
Expand DDoS Defenses
Increase defenses and mitigation capacity based on attack learnings. Bolster bandwidth, load balancing, caching, ACLs and other layers as needed against identified threat vectors.
Validate Backups and Archives
Verify backup systems maintained data integrity and accessibility through the attack. Test restoration of critical systems and data as part of recovery testing.
Tuning and Optimization
Use insights from the attack to fine tune defenses. Strengthen monitoring, alerts, and controls to quickly detect and stop future attacks before they spread.
Assess Legal Options
Explore legal recourse in response to the business impact and costs inflicted by the attack. Seek criminal charges and civil damages where feasible.
Recovering quickly from DDoS attacks minimizes business disruption and revenue loss while enhancing defenses against future incidents.
Conclusion
DDoS attacks remain a persistent threat, but their impacts can be minimized through robust defenses and quick recovery capabilities. A layered security strategy combined with continuous traffic monitoring, attack analysis and emergency response planning are critical. Leveraging massive DDoS mitigation services can provide the capacity needed to absorb volumetric and multi-vector attacks.
While attackers and botnets continue to evolve, organizations can help protect their business, customers and partners from DDoS disruptions through proactive measures and rapid response processes. Developing playbooks to maintain services throughout attacks and validating them through testing is key. With proper diligence and collaboration across security teams, infrastructure groups and executives, businesses can reduce their risks and strengthen confidence in withstanding DDoS attacks.
