"Unlimited defense" frequently appears in IDC service provider advertisements. How should this concept be understood? Can unlimited defense truly withstand DDoS attacks of any size? "Unlimited defense" is more of a marketing term than a rigorous technical promise. Any defense has physical and technical limitations. The core principle of Hong Kong high-defense servers is to separate attack traffic from normal business traffic through a distributed traffic scrubbing center.

When attack traffic enters the scrubbing network, the system filters it based on behavioral analysis, fingerprint recognition, and reputation scoring. The problem is that scrubbing capabilities are limited by three hard constraints: the total inbound bandwidth of the scrubbing center, the packet processing capacity of the cluster, and the accuracy of attack signature identification.

True "high-defense" is a combined solution: sufficient bandwidth reserves + intelligent scrubbing algorithms + rapid elastic scaling mechanisms. The "unlimited" promises made by service providers usually refer to no extra charges based on the size of the attack traffic during the contract period, or that their resource pool can elastically scale according to the attack scale. However, scaling takes time and still has theoretical limits.

How attacks bypass or penetrate defenses

Attackers' methods are constantly evolving. Faced with defenses, they primarily employ three strategies: bypass, penetration, and saturation.

"Bypass" attacks target blind spots in the defense system. For example, many scrubbing systems are slow to identify millions of "short-connection CC attacks" per second. These attacks simulate a massive number of legitimate users, rapidly establishing and disconnecting connections, exhausting the server's connection table resources.

# Simplified principle of simulating a CC attack (This is an illustration of the attack principle; please do not use it for illegal purposes)

# Attackers control a botnet to frequently initiate seemingly normal HTTP requests using real IPs

for i in {1..10000}; do

curl -s --connect-timeout 2 http://target website/a dynamic page &

done

# A large number of concurrent connections consume server resources, even if the traffic per connection is small.

"Penetrating" attacks exploit application-layer vulnerabilities. Attackers meticulously forge seemingly legitimate requests, such as credential brute-force attacks on login interfaces or slow query attacks on search functions. These requests can easily pass through traffic-based filters because they are indistinguishable from normal requests at the protocol level.

The most lethal attack is the "saturation" attack. Attackers mobilize botnets to launch multi-vector hybrid attacks, simultaneously impacting the network layer (such as SYN Flood), transport layer, and application layer. Even if the scrubbing center can handle 99% of the traffic, if the remaining 1% still far exceeds the origin server's capacity, service will still be interrupted. This type of attack aims to simultaneously test bandwidth, processing power, and algorithmic intelligence.

The Hidden Costs and Business Impact of Defense

Even if the defense successfully "blocks" the attack, the business may still suffer. The scrubbing process itself introduces additional network latency. Data packets need to be routed to the scrubbing center, analyzed, and then transmitted back to the origin server. This detour can add tens to hundreds of milliseconds of latency, which is fatal to services such as real-time gaming and financial transactions.

Another often overlooked impact is false positives during the scrubbing process. Any filtering algorithm has a false positive rate, especially when dealing with new or complex attacks. Some legitimate users may be blocked because their IPs are incorrectly blacklisted or their behavior patterns trigger rules, leading to business losses and a degraded user experience.

From a cost perspective, the defense resources provided by service providers are not free. "Unlimited defense" usually implies high fixed costs or implicit "fair use" terms. When the duration and scale of an attack exceed expectations, the service provider may implement traffic throttling or require an upgrade to a more expensive plan.

Real-world scenario analysis of defense failure

There is no invincible defense, only attacks that haven't reached their limits. Defense systems are prone to failure in the following scenarios:

When attack traffic instantly reaches and exceeds the maximum throughput of the scrubbing cluster, network ingress becomes congested, and normal traffic is dropped along with attack traffic. The scrubbing system, like a dam overflowing, becomes ineffective.

When attacks target DNS infrastructure or BGP routing, defenses may completely fail. If an attacker successfully attacks the DNS resolution service of a Hong Kong high-defense server or redirects traffic to an unprotected path through route hijacking, even the strongest server defenses are useless.

Internal vulnerabilities or misconfigurations are another fatal weakness. If an attacker gains server privileges through other means (such as social engineering or application vulnerabilities) or leaves open ports on the firewall due to misconfiguration, the defense becomes ineffective.

A Pragmatic Strategy for Building Effective Defenses

Instead of pursuing the myth of "invincibility," it's better to establish a layered, resilient defense system. First, accurately assess the actual needs of your business. The defense level required for a corporate website is completely different from that of an online game. Clearly defining the tolerable latency and downtime for core business operations is crucial for developing a reasonable defense budget and plan.

Second, adopt a hybrid defense architecture. Combine cloud-based high-defense services (for absorbing and mitigating large-scale attacks) with on-premises devices (for granular application-layer protection) to achieve complementary advantages. Simultaneously, ensure that there are backup plans to switch to if any single defense point fails.

Deploy comprehensive monitoring, monitoring not only server load and bandwidth but also key business metrics (such as login success rate and transaction latency). Establish clear emergency response procedures, including when to activate backup links and when to contact service providers to upgrade defenses.

Most importantly, recognize that security is an ongoing process. Regularly conduct penetration tests and attack/defense drills to simulate various attack scenarios, verify the effectiveness of the defense system, and identify weaknesses. Maintain close communication with defense service providers to stay informed about their technology updates and threat intelligence.