Connection timeout attacks – IP stresser’s impact on network stability

IP stressers are services that allow users to perform distributed denial-of-service (DDoS) attacks. They work by enlisting a large network of compromised devices that then be used to flood targets with fake traffic, typically TCP, UDP, or HTTP requests, with the goal of exhausting resources and making services unavailable.

Stressers allow attackers with limited technical knowledge to carry out powerful attacks by simply entering the target’s IP address or URL into a web-based interface. Attackers also specify attack types, duration, and intensity. The stresser service then handles everything else automatically. Some popular attack types stressers use include TCP floods, UDP floods, and HTTP floods. Many IP stresser services enlist tens or even hundreds of thousands of devices to participate in an attack. It provides enough bandwidth to overwhelm the defenses of most networks through sheer volume.

Connection timeout attack vector

A specific class of stresser-driven attacks that poses a severe threat involves timeouts. As networks and applications have improved protections against traditional protocol-based DDoS activities, attackers have innovated new attack types to bypass defense systems. The connection timeout attack aims to exploit TCP protocol weaknesses to consume connection resources. TCP is a foundational protocol that manages reliable communications and data transfer over IP networks. 

When initiating a TCP connection, a client sends a SYN packet to the server. The server responds with a SYN-ACK packet, and then the client confirms with an ACK packet. This 3-way handshake establishes the connection. Each connection utilizes server resources like memory, buffers, CPU capacity, and more. Servers have a finite ability to maintain open connections simultaneously. Once resource limits are reached, the server will be unable to establish any new connections until existing ones time out – usually after 60-120 seconds of inactivity.

This creates an opportunity for abuse. Attackers use IP Stresser to flood targets with TCP SYN requests. They never transmit the final ACK packet to complete the 3-way handshake. Servers queue up these half-open connections while they wait in vain for the ACK that finalizes them. With only a few bogus SYN requests, resource limits quickly be reached. The target is then unable to accept legitimate user traffic, causing denial-of-service. Because connections require over a minute each to time out, the effect lasts long after the bogus SYNs stop arriving. Attackers use this to maximize impact for minimal effort. The effect on targets is the same as any denial-of-service attack services become slow, unresponsive, or completely unavailable. Connection timeout attacks entail high operational, financial, and reputational costs.

Defending against connection timeout attacks

• Increased resource allocation – Expanding available connections through vertical or horizontal scaling improves resilience against consumption attacks. More connections take longer to fill up.
• Load balancers – Distributing traffic across multiple servers avoids overloading any single system’s resource capacity during attacks.
• Connection rate limiting – Restricting the number of connections allowed per client over time reduces exposure from high-volume attacks.
• Null routed IPs – Blacklisting known stresser IP ranges prevents them from accessing networks to conduct attacks.

Many solutions require extensive monitoring, analysis, and infrastructure configuration changes highlighting the importance of proactive security planning for connection timeout attacks.