how to prevent ddos attacks on linux server

Such an attack would seem to the server like someone hitting refresh on the same page multiple times. Application layer attacksĪpplication layer or layer 7 attacks target, as the name suggests, applications – the layer where the server generates web pages and responds to HTTP requests. It floods the network with an excessive number of incomplete, fragmented packets. The “too many packets” exploit is an example of a fragmentation attack. A fragmentation attack sends fake data packets that distort the flow of data and therefore overwhelm the server. They travel and are reassembled in different ways depending on whether the TCP or UDP transport protocol is being used. Traffic sent over the internet is divided into data packets. The attack is structured so that when DNS server responds, it sends more data to the victim than they can handle. One example of the volumetric attack could be the hacker spoofing the victim's IP and making multiple requests to an open DNS server. This is mostly done by using botnets and directing them to a specific target. It simply consumes all available bandwidth between the target and the internet. Volumetric attacks are the most common type of DDoS attack. The hacker keeps flooding it with more handshakes, eventually making it crash. This means the server cannot take any other requests. In this attack, the handshake is initiated, but the hacker leaves the server hanging and the ports open. TCP connection attacks, otherwise known as SYN flood attacks, happen when a three-way TCP handshake between the host and the server is never completed. Types of DDoS attacks TCP Connection attacks These attacks include SYN Floods, UDP Floods, and TCP Connection Exhaustion. Attacks that are on this layer include Smurf Attacks, ICMP Floods, and IP/ICMP Fragmentation. Most DDoS attacks happen in the following three layers: Every connection made over the internet goes through OSI model layers. This makes it even harder to distinguish between genuine and malicious traffic.ĭDoS attacks can target a specific component of the network connection or a mixture of them. The traffic bombarding the target is coming from legitimate (albeit infected) devices. Your computer might be a part of a botnet army, secretly responding to malicious commands, and you won’t even know - it’s hard to notice, as the only signs could be marginally decreased performance or an overheating device. This can cause a service to crash.ĭDoS attacks can last over 24 hours and are difficult to trace. A hacker creates a network by infecting devices, turning them into bots, and remotely directing them to a specific IP address all at once. DDoS attacks are quite powerful, as they use multiple computers or other devices.

How to prevent ddos attacks on linux server