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An Overview Of The Concept Of Syn Flooding In Cybersecurity

By Tom Seest

What Is Syn Flooding In Cybersecurity?

SYN flooding is a type of DoS attack that targets servers handling incoming TCP connections, such as web servers, email servers and infrastructure devices like firewalls.
The threat actor sends repetitive SYN packets to the server, often using a forged IP address. The server responds to these repeated requests with an SYN-ACK packet.

This photo was taken by Tima Miroshnichenko and is available on Pexels at https://www.pexels.com/photo/woman-in-sitting-on-chair-using-a-computer-5380592/.

What Is a Syn Flood In Cybersecurity?

A SYN flood is a type of denial-of-service (DoS) attack that targets servers and other internet infrastructure components. Botnets may use SYN floods to target load balancers, firewalls, and intrusion prevention systems (IPSs), reducing server capacity and interrupting services.
Every day, your computer communicates with other computers over the internet by sending and receiving synchronization messages. This three-step process starts with a SYN (or synchronize) message from your side, followed by an ACK response from theirs.
However, in a SYN flood attack, the malicious client sends multiple SYN requests to all of the server’s ports without ever returning an ACK packet. This makes it appear as if the connection is valid to the server.
Furthermore, a spoofed IP address is unrecognized by the server, meaning it cannot close the connection. Therefore, the server remains busy with hostile clients SYN flood attacks and keeps its connection state table full for as long as the attack persists.
SYN flooding is a type of TCP state-exhaustion attack that consumes the connection state table of the victim server, causing it to time out legitimate traffic packets, disconnect, or even reboot. SYN flooding attacks are widespread forms of DDoS that can take down any network that relies on TCP for communication – including web servers, email servers, database servers, and application servers – by disrupting its availability.
SYN flooding is becoming an increasingly popular DDoS attack method due to its ease of execution. It can be carried out directly or through a botnet of infected computers.
Direct SYN flood attacks are conducted from a single device with an actual IP address, making it easier to pinpoint their origin. To mitigate the attack, block the attacker’s IP address and restrict traffic coming from the compromised machine.
Distributed SYN flood attacks are more difficult to protect against as they involve a botnet of infected computers that spreads malicious traffic across multiple machines. While it’s usually possible to spoof their IP addresses with these botnets due to the sheer volume of traffic they generate, this may not always be feasible.

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How Does a Syn Flood Work In Cybersecurity?

SYN flooding is a type of denial-of-service (DoS) attack that utilizes repeated initial connection request (SYN) packets to overburden a server’s resources. These requests consume the server’s available ports, causing it to respond slowly or not at all to legitimate traffic.
A SYN flood attack is an easy method: malicious actors send numerous SYN packets from fake IP addresses to open ports on a targeted server, unaware that each request for SYN has been sent. When the server sends back its SYN-ACK response packet, however, due to spoofing of the IP address in each SYN packet, it does not receive it at all from the malicious client.
Each SYN-ACK packet is stored in the TCP connection table of a server, which eventually fills up and prevents further SYN packets from arriving from any source. This type of attack is frequently employed by botnets.
A SYN flood occurs when attackers spoof IP addresses on their SYN packets to circumvent mitigation efforts and make detection difficult. Alternatively, they use a botnet of infected machines to spread the attack across multiple network nodes.
A SYN flood differs from an ICMP flood in that it doesn’t attempt to overwhelm a server with excessive traffic. Instead, it pings all computers within the network in an effort to magnify its effect.
To prevent a SYN flood, administrators should increase a server’s backlog queue capacity, set it to recycle the oldest half-open TCP connection, and utilize SYN cookies to identify legitimate clients connecting to a target. Furthermore, firewalls and intrusion detection systems can be utilized as tools to mitigate this threat.
SYN flood attacks are often carried out by bots to conceal their identities and reduce the effort needed to track them down. They’re sometimes referred to as distributed DoS attacks due to multiple devices involved, and regardless of the method employed, they can cause significant harm to networks and infrastructure, impacting data, applications, and e-commerce sites alike. Depending on how severe the attack is, organizations may face loss of sales, reputation damage, disruption to critical infrastructure, or loss of business continuity.

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How Can You Prevent a Syn Flood In Cybersecurity?

SYN flooding is a type of denial-of-service attack that leverages the TCP handshake protocol to overwhelm servers. These assaults often target web and email servers as well as infrastructure devices like firewalls and load balancers.
A SYN flood is designed to overload a server with an excessive number of connection requests, causing it to respond slowly or not at all to legitimate traffic. This can cause significant disruption in network performance as well as financial losses and data loss.
To prevent an SYN flood, you need to take a defense-in-depth approach to cybersecurity. This involves installing multiple layers of protection, such as firewalls and intrusion detection systems. Furthermore, regularly patch your systems and monitor network traffic for suspicious activity.
An SYN flood occurs when an attacker repeatedly sends SYN packets to each port on a targeted server, usually using a spoof IP address. These SYN packets appear as valid TCP connections and are answered with an ACK from the server; however, this ACK packet never reaches the hostile client, leaving it half-open and consuming resources.
Due to a spoofed IP address, the server does not know that it has a connection and cannot close it by sending RST (reset) packets to the hostile client. Once SYN flood has exhausted all available ports on the server, it becomes unable to handle real users and ceases functioning properly.
Alternatively, an attacker could use a malicious client program that sends multiple SYN requests to all open ports on the target server. Since the server does not respond to each incoming request with an SYN-ACK packet, this hostile client can continue sending SYN packets until an ACK packet is received and the connection is closed.
This is known as a half-open connection and occurs for operating systems that do not have enough memory to store all incoming SYN packets. When your system experiences high demand from SYN floods, this can become overloaded and drain valuable resources. To mitigate this effect, increase the backlog queue limit on your system; though this may result in slower overall performance, it is better than being overwhelmed by SYN flooding.

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What Can You Do to Prevent a Syn Flood In Cybersecurity?

SYN flooding is a type of denial-of-service (DoS) attack that consumes the connection state table on a server by flooding it with TCP initial connection requests. This cyberattack has the potential to take down network devices, load balancers, session management servers, and other infrastructure components capable of supporting millions of connections – like web servers, email servers, or cloud-based server environments – by overloading them with TCP initial connection requests.
SYN flood attacks are caused by a malfunction with the TCP three-way handshake protocol. This protocol establishes a connection between the client and server by sending out an SYN packet, receiving an ACK response, and then completing the sequence number. In an SYN flood attack, however, an attacker repeatedly sends SYN packets without receiving an ACK, leading all communications ports on the target server to become half open – preventing it from completing its connection.
Attackers can also alter the source IP address in each SYN packet so the server doesn’t recognize they were targeted. This helps prevent incoming connections from being denied and makes tracing the malicious client’s origin much harder.
Network administrators can take measures to mitigate an SYN flood by altering TCP stacks by decreasing timeouts until memory is freed for each connection, or they can selectively drop incoming connections. They may also implement anti-spoofing or snooping policies as additional safeguards against malicious actors on their networks.
One of the most efficient methods to prevent an SYN flood is by employing multiple technologies that can detect and respond in real-time to such attacks. These include intrusion prevention systems (IPSs), firewalls, and load balancers – all of which monitor connection activity to shield your network from this type of attack.
An SYN flood attack can be costly, damaging, and frustrating for your network. That is why F5 DDoS protection solutions exist: they guarantee that your servers, apps, and infrastructure won’t be affected by this type of assault.
In an SYN flood attack, the malicious client sends SYN requests to all ports on a server using either fake or spoofed IP addresses. These requests appear to be legitimate TCP connections, and the server responds with SYN-ACK messages for each port. As these open connections accumulate, however, the server’s connection state tables become full of SYN-ACK requests from legitimate clients, leading it either to crash or cease responding to legitimate traffic altogether.

This photo was taken by Tima Miroshnichenko and is available on Pexels at https://www.pexels.com/photo/man-in-black-hoodie-using-computer-5380601/.