WK3 Secure Networks against Denial of Service attacks: Denial of Service attacks Flashcards
Denial of Service Attacks (DoS)
A denial of service attack is an attack that targets a network or server and floods it with network traffic. The objective of a denial of service attack, or a DoS attack, is to disrupt normal business operations by overloading an organization’s network.
The goal of the attack is to send so much information to a network device that it crashes or is unable to respond to legitimate users. This means that the organization won’t be able to conduct their normal business operations, which can cost them money and time. A network crash can also leave them vulnerable to other security threats and attacks.
Distributed denial of service attack (DDoS)
A distributed denial of service attack, or DDoS, is a kind of DoS attack that uses multiple devices or servers in different locations to flood the target network with unwanted traffic. Use of numerous devices makes it more likely that the total amount of traffic sent will overwhelm the target server.
An unfortunate example I’ve seen is an attacker who crafted a very careful packet that caused a router to spend extra time processing the request. The overall traffic volume didn’t overload the router; the specifics within the packet did.
3 common Network level DoS attacks
- SYN flood attack
Target network bandwidth to slow traffic.
A SYN flood attack is a type of DoS attack that simulates the TCP connection and floods the server with SYN packets.
Let’s break this definition down a bit more by taking a closer look at the handshake process that is used to establish a TCP connection between a device and a server. The first step in the handshake is for the device to send a SYN, or synchronize, request to the server. Then, the server responds with a SYN/ACK packet to acknowledge the receipt of the device’s request and leaves a port open for the final step of the handshake. Once the server receives the final ACK packet from the device, a TCP connection is established.
Malicious actors can take advantage of the protocol by flooding a server with SYN packet requests for the first part of the handshake. But if the number of SYN requests is larger than the number of available ports on the server, then the server will be overwhelmed and become unable to function.
3 common Network level DoS attacks
- ICMP
ICMP stands for Internet Control Message Protocol.
ICMP is an internet protocol used by devices to tell each other about data transmission errors across the network. Think of ICMP like a request for a status update from a device. The device will return error messages if there is a network concern. You can think of this like the ICMP request checking in with the device to make sure that all is well. An ICMP flood attack is a type of DoS attack performed by an attacker repeatedly sending ICMP packets to a network server. This forces the server to send an ICMP packet. This eventually uses up all the bandwidth for incoming and outgoing traffic and causes the server to crash.
Both of the attacks we’ve discussed so far, SYN flood and ICMP flood, take advantage of communication protocols by sending an overwhelming number of requests. There are also attacks that can overwhelm the server with one big request. One example that we’ll discuss is called the ping of death.
3 common Network level DoS attacks
- A ping of death attack
A ping of death attack is a type of DoS attack that is caused when a hacker pings a system by sending it an oversized ICMP packet that is bigger than 64 kilobytes, the maximum size for a correctly formed ICMP packet.
Pinging a vulnerable network server with an oversized ICMP packet will overload the system and cause it to crash.
Think of this like dropping a rock on a small anthill. Each individual ant can carry a certain amount of weight while transporting food to and from the anthill. But if a large rock is dropped on the anthill, then many ants will be crushed, and the colony is unable to function until it rebuilds its operations elsewhere.
