Proxy servers act as critical intermediaries in modern network architectures, facilitating secure data transfer, anonymity, and access control. However, their role as traffic gatekeepers also makes them prime targets for Distributed Denial of Service (DDoS) attacks. A successful DDoS attack on a proxy server can cripple network operations, disrupt services, and expose sensitive data—costing organizations millions in downtime and recovery. In this guide, we’ll break down actionable strategies to harden proxy servers against DDoS threats, explore key features of resilient proxy services, and explain why choosing a provider like OwlProxy is critical for long-term security. Whether you’re managing enterprise proxies or optimizing personal privacy, these insights will help you build a defense that stands up to even sophisticated DDoS campaigns.
Understanding DDoS Attacks on Proxy Servers: Risks and Impact
Before diving into hardening techniques, it’s essential to grasp why proxy servers are vulnerable to DDoS attacks and the specific risks they face. Unlike standalone servers, proxy servers handle traffic on behalf of multiple clients, amplifying their exposure to malicious activity. Attackers target proxies for three primary reasons: to disrupt downstream services (e.g., a web server protected by the proxy), to exhaust the proxy’s resources and render it useless, or to expose the proxy’s IP address and use it as a launchpad for further attacks.
DDoS attacks on proxies typically fall into three categories, each with distinct mechanisms and impacts:
Volumetric Attacks: These floods the proxy with massive amounts of junk traffic—often gigabits or terabits per second—to saturate bandwidth and overwhelm network interfaces. For example, a botnet sending UDP packets to random ports can consume all available bandwidth, preventing legitimate traffic from reaching the proxy. Proxies with limited upstream bandwidth are particularly susceptible, as even a moderate volumetric attack can cause latency spikes or complete outages.
Protocol Attacks: These exploit weaknesses in network protocols (e.g., TCP, ICMP) to exhaust the proxy’s processing resources. A common example is a SYN Flood, where attackers send incomplete TCP handshake requests (SYN packets) to the proxy, leaving half-open connections that consume memory and CPU. Over time, these connections pile up, blocking the proxy from accepting new legitimate requests. Other protocol attacks include ICMP Echo Requests (ping floods) and fragmented packet floods, which force the proxy to waste resources reassembling malformed data.
Application-Layer Attacks: Targeting the proxy’s application logic (e.g., HTTP, DNS), these attacks are harder to detect and often mimic legitimate user behavior. For instance, a Slowloris attack sends partial HTTP requests to keep connections open indefinitely, tying up the proxy’s connection pool. Similarly, attackers may use HTTP POST floods to overload the proxy with large data payloads, exhausting disk I/O or memory. Application-layer attacks are particularly dangerous because they require fewer resources to execute—even a small botnet can disrupt a proxy by targeting its application stack.
The consequences of an unhardened proxy server falling victim to DDoS are severe. For enterprises, downtime can lead to lost revenue, damaged customer trust, and regulatory penalties (e.g., GDPR violations for service interruptions). For individual users or small businesses, a DDoS attack on a personal proxy can result in IP blacklisting, identity theft, or exposure of sensitive data (e.g., login credentials). In some cases, attackers may even leverage compromised proxies to launch secondary attacks on internal networks, turning the proxy from a security tool into a vulnerability.
To mitigate these risks, organizations must adopt a layered approach to proxy hardening—combining network-level defenses, application-layer safeguards, and intelligent resource management. Equally important is selecting a proxy service provider with built-in DDoS resilience, as not all proxies are designed to withstand attacks. Later in this guide, we’ll explore how services like OwlProxy address these vulnerabilities through features like global IP diversity, elastic scaling, and enterprise-grade traffic filtering.
Core Strategies to Harden Proxy Servers Against DDoS
Network-Level Protection: Blocking Attacks at the Edge
Network-level protection forms the first line of defense against DDoS attacks, focusing on filtering malicious traffic before it reaches the proxy server. This layer is critical because volumetric and protocol attacks often target the network infrastructure itself, and stopping them early reduces the load on downstream systems. Below are key techniques to implement at the network layer:
Deploy DDoS Protection Appliances: Hardware-based solutions like Next-Generation Firewalls (NGFWs), Intrusion Prevention Systems (IPS), and dedicated DDoS mitigation appliances (e.g., Arbor Networks, Radware) are designed to identify and block malicious traffic in real time. These devices use signature-based detection (matching known attack patterns) and behavioral analysis (flagging anomalies like sudden traffic spikes) to filter out threats. For example, an NGFW can be configured to drop SYN packets exceeding a threshold rate or block UDP floods from known botnet IP ranges. When selecting appliances, prioritize those with high throughput (10+ Gbps) to handle large-scale volumetric attacks.
Implement Traffic Cleansing and Scrubbing: Traffic cleansing involves routing incoming proxy traffic through a specialized scrubbing center, where malicious packets are identified and removed before clean traffic is forwarded to the proxy. This is particularly effective against volumetric attacks, as scrubbing centers can handle terabits of traffic and separate legitimate requests from junk data. Many cloud-based proxy providers (including OwlProxy) integrate with global scrubbing networks, ensuring that even if an attack targets a specific region, traffic is rerouted through unaffected cleansing nodes. For on-premises proxies, organizations can partner with DDoS mitigation services (e.g., Cloudflare, Akamai) to offload traffic scrubbing.
Adopt Anycast Networking: Anycast is a network routing technique where multiple servers share the same IP address, and traffic is routed to the nearest (or least congested) server in the network. For proxy servers, Anycast distributes traffic across a global network of nodes, making it harder for attackers to overwhelm a single point of failure. If one node is targeted by a DDoS attack, traffic automatically reroutes to other nodes, minimizing downtime. Anycast is especially effective against volumetric attacks, as the attack traffic is spread thin across multiple servers. OwlProxy leverages Anycast in its global node network, ensuring that proxy traffic is always routed through the most resilient path.
Configure Rate Limiting and Connection Throttling: Rate limiting restricts the amount of traffic a single IP address or client can send to the proxy, preventing individual sources from overwhelming the server. For example, setting a rate limit of 100 requests per minute per IP blocks botnets that generate thousands of requests from a single source. Connection throttling, on the other hand, limits the number of concurrent connections a client can establish—critical for mitigating application-layer attacks like Slowloris. Most proxy servers (e.g., Nginx, Squid) support rate limiting via modules (e.g., ngx_http_limit_req_module for Nginx), allowing administrators to define thresholds based on IP, user agent, or request type.
Use Blacklisting and Whitelisting: IP blacklisting blocks traffic from known malicious sources (e.g., botnet C2 servers, previously identified attackers), while whitelisting allows only trusted IPs to access the proxy. Blacklists should be regularly updated using threat intelligence feeds (e.g., Spamhaus, MISP) to stay ahead of new threats. However, over-reliance on blacklisting can lead to false positives, so combining it with whitelisting for critical clients (e.g., internal IPs) adds an extra layer of security. For dynamic environments, consider geoblocking—restricting proxy access to specific regions unless necessary (e.g., a U.S.-based business blocking traffic from high-risk countries).
Application-Level Defense: Securing the Proxy’s Logic Layer
While network-level measures block large-scale attacks, application-layer defenses protect the proxy’s software stack from targeted, low-volume threats. These techniques focus on validating requests, securing protocols, and hardening the proxy’s codebase to prevent exploitation. Here’s how to implement them:
Secure Proxy Protocols and Versions: Outdated or unpatched proxy software is a common entry point for attacks. Ensure your proxy server runs the latest stable version of its software (e.g., Squid 5.x, Nginx 1.25+) and disable unnecessary protocols or features. For example, if your proxy only needs to support HTTP/HTTPS, disable FTP or SOCKS4 support to reduce the attack surface. Additionally, enforce secure protocol versions: use TLS 1.3 for HTTPS, disable SSLv3 and TLS 1.0/1.1 (vulnerable to POODLE and BEAST attacks), and configure strong cipher suites (e.g., ECDHE-ECDSA-AES256-GCM-SHA384). For SOCKS proxies, use SOCKS5 instead of SOCKS4, as it supports authentication and encryption.
Implement Request Validation and Sanitization: Application-layer attacks often exploit malformed requests, so validating incoming data is critical. For HTTP proxies, use web application firewalls (WAFs) like ModSecurity to inspect and block malicious requests. WAF rules can detect SQL injection, cross-site scripting (XSS), and path traversal attempts—common techniques used to compromise proxy servers. Additionally, sanitize request headers (e.g., User-Agent, Referer) to block spoofed or malformed values, and enforce strict content-length limits to prevent large payload floods. For example, limiting POST requests to 1MB per client thwarts HTTP POST flood attacks.
Enable Strong Authentication and Access Control: Unauthenticated proxies are easy targets for attackers, who can use them to anonymize their own DDoS traffic. Require clients to authenticate before using the proxy, using methods like username/password (with hashing via bcrypt or Argon2), API keys, or client-side certificates. For enterprise proxies, integrate with identity providers (IdPs) like LDAP or OAuth2 for centralized access control. Additionally, implement role-based access control (RBAC) to restrict proxy features based on user roles—e.g., limiting “admin” users to configuration changes and “standard” users to basic traffic forwarding. OwlProxy enhances security by supporting multiple authentication methods across its proxy types, ensuring only authorized users can access its network.
Optimize Caching and Connection Management: Caching frequently requested content reduces the proxy’s load and mitigates application-layer attacks by serving cached responses instead of processing new requests. Configure the proxy to cache static assets (e.g., images, CSS) with appropriate TTLs (time-to-live) and avoid caching dynamic content (e.g., login pages) that could leak sensitive data. For connection management, set timeouts for idle connections (e.g., 30 seconds for HTTP) to prevent Slowloris-style attacks, and use connection pooling to reuse existing connections, reducing overhead. Tools like Nginx’s keepalive directive or Squid’s persistent connections feature can help optimize connection handling.
Harden the Proxy Server’s Operating System: The proxy’s underlying OS is a critical component of its security. Disable unnecessary services (e.g., Telnet, FTP) and daemons (e.g., cups, avahi) to reduce attack surface, and configure the OS firewall (e.g., iptables, ufw) to block unused ports. Use secure file permissions (e.g., chmod 600 for configuration files) and limit user privileges—run the proxy process as a non-root user to minimize damage if compromised. Additionally, enable logging and auditing tools (e.g., auditd, syslog-ng) to track system changes and detect unauthorized access attempts. Regularly update the OS and its packages to patch vulnerabilities like buffer overflows or privilege escalation bugs.
Resource Allocation and Scalability: Ensuring Sustained Performance Under Attack
Even with robust protection measures, a proxy server can fail under DDoS pressure if its resources are insufficient. Proper resource allocation and scalability ensure the proxy can absorb attacks while maintaining service for legitimate users. Here’s how to optimize resource management:
Right-Size Hardware and Infrastructure: Proxies handling high traffic volumes or critical workloads require adequate CPU, memory, and storage. For on-premises proxies, use multi-core processors (8+ cores) to handle concurrent connections, and allocate sufficient RAM (16GB+ for enterprise use) to cache content and manage connections. Use SSDs instead of HDDs for faster I/O, reducing latency during attacks. For cloud-based proxies, choose instance types optimized for network performance (e.g., AWS c5n, Google Cloud n2-highcpu) and avoid overcommitting resources—oversubscription leads to contention during traffic spikes. Many organizations opt for hybrid models, combining on-premises proxies with cloud scaling to handle variable loads.
Leverage Elastic Scaling and Load Balancing: Elastic scaling allows the proxy infrastructure to add or remove resources dynamically in response to traffic changes. Cloud-based proxies (e.g., those offered by OwlProxy) excel here, as they can spin up new proxy instances within minutes to handle DDoS traffic. Load balancers distribute traffic across multiple proxy servers, preventing any single instance from being overwhelmed. Use layer 4 (TCP/UDP) load balancers for network-level distribution and layer 7 (HTTP) load balancers for application-level routing (e.g., directing traffic based on URL or user agent). Additionally, implement health checks to automatically remove unresponsive proxies from the pool, ensuring traffic is only sent to healthy instances.
Implement Resource Isolation: Isolating proxy resources prevents attacks on one service from affecting others. For example, using virtual machines (VMs) or containers (Docker, Kubernetes) to separate proxy instances by client, application, or traffic type. If a DDoS attack targets a proxy handling customer traffic, isolated VMs ensure internal traffic (e.g., employee web browsing) remains unaffected. For multi-tenant proxies, use cgroups (Linux Control Groups) to limit CPU, memory, and I/O per tenant, preventing one client from monopolizing resources. Resource isolation also simplifies monitoring, as anomalies in one group are easier to identify and contain.
Optimize Bandwidth and Traffic Prioritization: Bandwidth is a finite resource, so prioritizing legitimate traffic during DDoS attacks is essential. Use quality of service (QoS) tools to classify traffic based on importance—e.g., assigning high priority to business-critical applications (e.g., CRM, ERP) and low priority to non-essential traffic (e.g., video streaming). Traffic shaping techniques like packet scheduling (e.g., WFQ, CBWFQ) ensure high-priority traffic is processed first, even during congestion. Additionally, work with your ISP to implement upstream bandwidth limits or “black hole” routing—diverting malicious traffic to a null route before it reaches your proxy. For organizations with global operations, using a proxy provider with multiple upstream ISPs (like OwlProxy) reduces reliance on a single network, minimizing the impact of ISP-level outages.
Selecting DDoS-Resilient Proxy Services: Key Criteria and Comparisons
While in-house hardening is critical, the foundation of proxy DDoS resilience often lies in choosing the right service provider. Not all proxy services are built to withstand attacks—many prioritize cost or speed over security, leaving users vulnerable to downtime. To select a DDoS-resilient proxy service, focus on the following criteria, and see how OwlProxy compares to competitors in the table below.
IP Pool Size and Diversity: A large, diverse IP pool is essential for mitigating DDoS attacks, as it allows the proxy service to distribute traffic across multiple IPs and avoid single points of failure. Attackers often target specific IPs, so a provider with millions of IPs (e.g., dynamic residential proxies) can quickly rotate or replace compromised IPs, minimizing disruption. Additionally, global IP coverage ensures traffic can be rerouted through unaffected regions during regional attacks. Avoid providers with small or concentrated IP pools (e.g., 10k-100k IPs), as these are easier to saturate with DDoS traffic.
Built-In DDoS Mitigation Infrastructure: The best proxy providers integrate enterprise-grade DDoS mitigation into their networks, including traffic scrubbing centers, Anycast routing, and WAFs. Look for providers that partner with leading DDoS protection firms (e.g., Cloudflare, Akamai) or operate their own scrubbing facilities. Additionally, check if the provider offers automatic attack detection and mitigation—manual intervention delays response and increases downtime. Features like real-time traffic analysis, anomaly detection, and instant IP rotation are critical for fast threat response.
Protocol Support and Flexibility: DDoS attacks target multiple protocols, so the proxy service must support secure, modern protocols and allow flexibility in switching between them. SOCKS5, HTTP, and HTTPS are essential for most use cases, with SOCKS5 offering better performance for non-web traffic (e.g., gaming, P2P). Providers should allow clients to switch protocols without service interruptions—critical for adapting to attack patterns (e.g., switching from HTTP to SOCKS5 if HTTP ports are targeted). Additionally, support for both static and dynamic proxies ensures users can choose the right type for their needs: static proxies for stable, long-term connections and dynamic proxies for IP rotation during attacks.
Scalability and Pricing Flexibility: DDoS attacks are unpredictable, so the proxy service must scale with traffic spikes without exorbitant costs. Look for providers with pay-as-you-go pricing for dynamic proxies (pay per GB of traffic) and unlimited traffic options for static proxies (flat fee for a set duration). This flexibility ensures you only pay for what you use during attacks and avoids overage charges from sudden traffic increases. Additionally, check if the provider offers instant scaling—adding more IPs or bandwidth within minutes of an attack being detected.
Customer Support and SLA Guarantees: During a DDoS attack, responsive support can mean the difference between minutes and hours of downtime. Choose providers with 24/7 technical support via live chat, email, or phone, and look for service-level agreements (SLAs) that guarantee uptime (e.g., 99.9%+) and response times (e.g., < 15 minutes for critical issues). Avoid providers with limited support hours or vague SLAs, as these indicate a lack of commitment to reliability.
To illustrate these criteria, the table below compares OwlProxy with two common types of competitors: generic low-cost proxy providers and free proxy services (often associated with higher risks). Many users may initially consider free proxy options for cost savings, but free proxy services often lack basic security measures, leaving them vulnerable to DDoS attacks and IP blacklisting. In contrast, enterprise-grade solutions like OwlProxy prioritize both security and performance—explore the differences at https://www.owlproxy.com/.
Criteria | Free Proxy Services | Low-Cost Generic Providers | OwlProxy |
---|---|---|---|
IP Pool Size | Very small (1k-10k IPs); often shared publicly | Small to moderate (50k-500k IPs); limited diversity | Large (50m+ dynamic proxies, 10m+ static proxies); global coverage (200+ countries) |
DDoS Mitigation | None; no scrubbing or Anycast | Basic (rate limiting only); no dedicated scrubbing | Enterprise-grade (Anycast, traffic scrubbing, WAF integration); automatic attack detection |
Protocol Support | HTTP only; no encryption or authentication | HTTP/HTTPS; limited SOCKS5 support | SOCKS5, HTTP, HTTPS; protocol switching without interruption |
Scalability | Not scalable; fixed IPs, no bandwidth expansion | Limited; pre-paid plans with strict limits | Unlimited dynamic scaling; pay-as-you-go traffic (dynamic proxies); unlimited traffic (static proxies) |
Support & SLA | No support; no uptime guarantees | Email support only; 95% uptime SLA | 24/7 live chat/email support; 99.9% uptime SLA |
OwlProxy’s standout features include its massive IP pool, which ensures even large-scale DDoS attacks are diluted across thousands of nodes, and its flexible protocol support, allowing users to adapt to evolving threats. For example, if an attacker targets HTTP ports, OwlProxy users can switch to SOCKS5 with a few clicks, rerouting traffic through unaffected ports. Additionally, its dynamic proxies’ pay-as-you-go pricing ensures users don’t overpay for idle resources, while static proxies’ unlimited traffic model provides stability for long-term operations. To ensure your proxy infrastructure can scale during DDoS events, choosing a provider with a large IP pool and flexible resource allocation is critical—OwlProxy, for example, offers 50m+ dynamic proxies and 10m+ static proxies across 200+ countries, enabling seamless scaling to absorb traffic spikes.
Monitoring, Detection, and Incident Response for Proxy Security
Even the most hardened proxy server requires continuous monitoring and a well-defined incident response plan to stay ahead of DDoS attacks. Monitoring detects anomalies early, while incident response minimizes damage and ensures a quick recovery. This section outlines best practices for both.
Implementing Real-Time Monitoring Tools
Effective monitoring starts with the right tools to track key metrics and detect anomalies. For proxy servers, focus on the following metrics:
Traffic Volume and Bandwidth Usage: Sudden spikes in incoming/outgoing traffic (e.g., a 10x increase in 5 minutes) often indicate a volumetric DDoS attack. Use tools like Prometheus with Grafana, Zabbix, or Datadog to monitor bandwidth in real time and set alerts for deviations from baseline usage. For example, if your proxy typically handles 100 Mbps, an alert for traffic exceeding 500 Mbps can trigger an investigation.
Connection Metrics: Track the number of active connections, connection attempts, and connection failures. A surge in failed connections (e.g., SYN retransmissions) may signal a protocol attack like SYN Flood. Tools like netstat (Linux) or TCPView (Windows) provide real-time connection data, while proxy-specific logs (e.g., Squid access logs, Nginx error logs) offer insights into client behavior. Set thresholds for maximum concurrent connections per IP (e.g., 100 connections/IP) to detect application-layer attacks like Slowloris.
Resource Utilization: CPU, memory, disk I/O, and network interface usage are critical indicators of attack impact. High CPU usage (e.g., >90%) during low traffic periods may indicate a protocol attack (e.g., packet fragmentation), while memory leaks suggest application-layer exploitation. Use tools like top, htop, or SNMP-based monitors to track resource usage and set alerts for sustained high utilization (e.g., >80% CPU for 5+ minutes).
Proxy-Specific Metrics: Each proxy software has unique metrics worth monitoring. For Squid, track cache hit ratio (low ratios may indicate cache poisoning attempts), request latency (sudden increases suggest DoS), and client errors (4xx/5xx status codes). For Nginx, monitor upstream server health, request rate per worker process, and SSL handshake failures (indicators of SSL/TLS attacks). Integrate proxy logs with centralized logging tools like ELK Stack (Elasticsearch, Logstash, Kibana) or Splunk for aggregated analysis and long-term trend tracking.
Anomaly Detection and Alerting
Monitoring tools generate vast amounts of data, so anomaly detection is essential to separate normal variations from malicious activity. Use the following techniques to identify attacks:
Baseline Behavior Analysis: Establish baseline metrics for traffic, connections, and resource usage during normal operation (e.g., average traffic at 9 AM, peak connections on weekends). Anomaly detection systems (ADS) compare real-time data to these baselines, flagging deviations beyond a threshold (e.g., 3 standard deviations). Machine learning-based ADS (e.g., Darktrace, ExtraHop) improve accuracy over time by learning patterns specific to your proxy environment.
Signature-Based Detection: Use known attack signatures to identify common threats. For example, rules in Snort or Suricata can detect SYN Floods (signature: high SYN packet rate with few ACKs), HTTP Slowloris (signature: partial requests with long timeouts), or DNS amplification attacks (signature: large DNS responses from small requests). Update signatures regularly via threat feeds to catch new attack variants.
Behavioral Analysis: Attackers often exhibit patterns like repetitive requests, unusual user agents, or requests to non-existent resources. Behavioral analysis tools flag these patterns—e.g., a single IP making 10,000 requests/minute to /login.php, or a User-Agent string matching a known botnet (e.g., “Mozilla/5.0 (compatible; EvilBot/1.0)”). Integrate threat intelligence feeds (e.g., AlienVault OTX, IBM X-Force) to enrich behavioral data with known malicious indicators (IOCs) like IPs, domains, or hashes.
Alert Prioritization: Not all alerts require immediate action, so prioritize them based on severity. Critical alerts (e.g., bandwidth exceeding scrubbing capacity) should trigger instant notifications (SMS, phone call), while warnings (e.g., 10% increase in failed connections) can be sent via email. Use tools like PagerDuty or Opsgenie to manage alert routing and ensure the right team members are notified based on the alert type and time of day.
Incident Response Planning for DDoS Attacks
A well-documented incident response (IR) plan ensures your team acts quickly and consistently during a DDoS attack. Follow these steps to build an effective plan:
Preparation: Define roles and responsibilities (e.g., IR team lead, network engineer, communication lead) and document contact information for key personnel and external partners (e.g., ISP, DDoS mitigation service). Preconfigure mitigation actions (e.g., IP blacklists, rate limit rules) and test them in a staging environment to ensure they work as intended. Train the team on proxy-specific procedures, such as rotating IPs in OwlProxy’s dashboard or enabling traffic scrubbing via the provider’s API.
Detection and Analysis: When an alert triggers, confirm the attack type (volumetric, protocol, application-layer) using monitoring data. For example, high bandwidth with UDP traffic suggests a volumetric attack, while high SYN packets indicate a protocol attack. Collect evidence (logs, traffic captures via tcpdump) for post-attack analysis and share details with the proxy provider—OwlProxy’s support team, for instance, can use this data to fine-tune mitigation for your specific case.
Containment: Activate preconfigured mitigation measures to limit attack impact. For volumetric attacks, redirect traffic to the provider’s scrubbing center or enable Anycast routing. For protocol attacks, apply rate limits or block malicious IPs via the firewall. For application-layer attacks, enable WAF rules or switch to a different proxy protocol. If the attack is severe, temporarily restrict access to critical clients only (via whitelisting) to ensure business continuity.
Eradication and Recovery: Once the attack is contained, remove malicious IPs from blacklists, reset rate limits, and restore normal proxy configuration. Scan the proxy server for signs of compromise (e.g., backdoors, malware) using tools like ClamAV or Lynis. Update proxy software and OS patches to address vulnerabilities exploited in the attack. For dynamic proxies, rotate IPs to avoid re-targeting, and for static proxies, consider switching to a new IP address if the old one is compromised.
Post-Incident Review: After recovery, conduct a “lessons learned” meeting to analyze the attack timeline, identify gaps in monitoring or mitigation, and update the IR plan. For example, if the attack went undetected for 30 minutes, adjust alert thresholds or add new metrics to monitor. Share findings with the proxy provider to improve their services—OwlProxy, for instance, uses customer feedback to enhance its anomaly detection algorithms.
FAQ:
Q: How do proxy servers become targets of DDoS attacks in the first place?
Proxy servers are targeted for DDoS attacks due to their role as intermediaries in network traffic. Attackers may target proxies to disrupt downstream services (e.g., a web server behind the proxy), use the proxy’s IP to anonymize their own malicious activity, or exhaust the proxy’s resources to render it useless for legitimate users. Additionally, proxies with exposed IP addresses (common in public or poorly configured private proxies) are easy targets for scanning and targeting. For example, if a proxy is used to scrape data from a competitor’s website, the competitor may launch a DDoS attack to block the scraping activity. Proxies with large user bases (e.g., public free proxies) are also attractive targets, as taking them down disrupts many users at once.