Denial-of-service (DoS) and distributed denial-of-service (DDoS) attacks

1. Denial-of-service (DoS) and distributed denial-of-service (DDoS) attacks

A denial-of-service attack overpowers a system's assets so it can't react to support demands. A DDoS attack is additionally an attack on the system's assets, however, it is dispatched from an enormous number of other host machines that are tainted by malicious software controlled by the attacker.

Dissimilar to attacks that are intended to empower the attacker to acquire or expand access, denial-of-service doesn't give direct advantages to attackers. For some of them, it's sufficient to have the fulfillment of service denial. Nonetheless, on the off chance that the assaulted asset has a place with a business contender, the advantage to the attacker might be sufficiently genuine. Another reason for a DoS attack can be to take a system disconnected with the goal that an alternate sort of attack can be dispatched.

TCP SYN flood attack:-

In this attack, an attacker abuses the utilization of the support space during a Transmission Control Protocol (TCP) session initialization handshake. The attacker's gadget floods the objective system's small in-process queue with association demands, yet it doesn't react when the objective system answers to those requests. This makes the objective system break while sitting tight for the reaction from the attackers' gadget, which makes the system crash or becomes unusable when the connection queue fills up.

There are a couple of countermeasures to a TCP SYN flood attack:

  • Spot servers behind a firewall designed to stop inbound SYN packets.
  • Increment the size of the connection queue and decrease the timeout on open connections.

Teardrop attack:-

This attack causes the length and fractures offset fields in consecutive Internet Protocol (IP) packets to cover each other on the attacked host; the attacked system endeavors to recreate packets during the cycle yet falls flat. The objective system then, at that point becomes befuddled and crashes. ,

On the off chance that clients don't have patches to ensure against this DoS assault, disable SMBv2 and block ports 139 and 445.

Smurf attack:-

This attack includes utilizing IP spoofing and the ICMP to soak an objective network with traffic. This attack strategy utilizes ICMP echo requests designated at broadcast IP addresses. These ICMP requests begin from a spoofed “victim” address.

For example, if the expected victim address is, the attacker would spoof an ICMP echo request from to the transmission address This request would go to all IPs in the reach, with every one of the reactions returning to, overpowering the organization. This interaction is repeatable and can be computerized to produce immense measures of network clog.

To shield your devices from this assault, you need to disable IP-directed broadcasts at the routers. This will forestall the ICMP echo broadcast request at the network devices. Another choice is to design the end system to hold them back from reacting to ICMP packets from broadcast addresses.

Ping of death attack:-

This sort of attack utilizes IP packets to 'ping an objective system with an IP size over the limit of 65,535 bytes. IP bundles of this site are not permitted, so the attacker fragments the IP packet. When the objective system reassembles the packets, it can encounter buffer overflows and different crashes.

Ping of death attacks can be hindered by utilizing a firewall that will check fragmented IP bundles for the most extreme size.


Botnets are the large numbers of systems tainted with malware under hackers' control to do DDoS attacks. These bots or zombie systems are utilized to complete attacks against the objective systems, regularly overwhelming the objective system's data transfer capacity and preparing abilities. These DDoS attacks are hard to trace because botnets are situated in varying geographic areas.

Botnets can be mitigated by:

RFC3704 filtering, which will deny traffic from spoofed addresses and help ensure that traffic is traceable to its correct source network. For example, RFC3704 filtering will drop packets from bogon list addresses.

Blackhole filtering, which drops undesirable traffic before it enters a protected network. When a DDoS attack is detected, the BGP (Border Gateway Protocol) host should send routing updates to ISP routers so that they route all traffic heading to victim servers to a null0 interface at the next hop.