![]() ![]() This is pretty much impossible from a TCP standpoint. Also, we are sending the target a time to live value of 0. In the previous command line, we are sending 2000 packets from our eth0 interface on our Kali server to the destination address 10.0.0.1. In this case we are sending 2000 packets using the command: send(IP(dst="10.0.0.1",ttl=0)/TCP(),iface="eth0",count=2000) Also, we are going to specify the number of packets we will send to our destination. In this use case, our test server is 10.0.0.1. In this following screenshot, we are going to use Scapy to send malformed TCP packets to our test server. Once scapy has been launched, type in command syntax: To start Scapy, type scapy in the terminal window. One common trick is to manipulate TCP packets from Kali and send it out via Scapy. ![]() Also, it can handle tasks such as scanning, tracerouting, probing, unit tests, attacks, and network discovery. Scapy can forge or decode packets, send them on the wire, capture them, and match requests and replies. Scapy is a packet manipulation tool for computer networks, written in Python by Philippe Biondi. One of the most popular DoS tools is Scapy. These attacks could severely damage a web site or web application: Remember, you should only attempt this on IPs and sites you ave permission to test. The second screenshot shows the successful handshakes, which will eventually DoS the target. ![]() ![]() In the following screenshot, we will show a website that doesn’t leverage SSL hence showing connection errors. Once THC-SSL-DOS is executed, you will see some funny verbiage stating it is starting and the handshake process being exploited. To run THC-SSL-DOS against a target, type t: thc-ssl-dos and -accept This will bring up a terminal window with the homepage for THC-SSL-DOS. To access THC-SSL-DOS, navigate to Stress Testing | Web Stress Testing | thc-ssldos. This is a known vulnerability, and no real solution exists to remediate this as of the writing of this text. The advantage of this approach is that the processing capacity for SSL handshakes is far superior at the client side, meaning that a common laptop over an average network connection can challenge a web application server. This is known as an SSL-Exhaustion attack. The attack exploits the SSL secure re-negotiation feature to trigger thousands of re-negotiations using a single TCP connection. THC-SSL-DOS exploits this asymmetric property by overloading the server until it is unable to provide any service to legitimate users. Establishing a secure SSL connection requires 15x more processing power on the server than client. The Secure Socket Layer (SSL) protocol is used to secure connections and transactions over the Internet. Here are a few more tools available in Kali Linux to perform DoS attacks: THC-SSL-DOS Also, Chapter 3 covered a popular Protocol DoS tool Scapy. Kali Linux contains multiple vulnerability exploitation tools covered in previous chapters that can be used for Application Layer DoS attacks such as Metasploit. Session Exhaustion: Abusing session limitations by repeatedly establishing but not closing new sessions with the goal of consuming resources.The examples include Zero-day attacks, vulnerability exploitation, and so on. Application Layer Attacks: It leverages legitimate traffic to crash a web service.Examples are SYN floods, Ping of death, Smurf, Teardrop, fragmented packets, and so on. Protocol Attacks: It consumes resources of servers or intermediate communication equipment, such as routers, firewalls, load balancers, and so on.The purpose is to saturate the bandwidth of the victim website. Volume Based Attacks: It involves UDP floods, ICMP floods, and other spoofed packet-based floods.There are four major DoS/DDoS attack categories: DoS attacks can target system resources (IE disk space, bandwidth, and so on), configuration information (IE remove route tables), state information (TCP session resetting), or anything that can harm system operation. This overload prevents the resource from responding to legitimate traffic, or slows its response so significantly that it is rendered unavailable. The most common DoS attack involves flooding a target with external communication requests. This is commonly termed as stress testing your Internet facing services. For this reason, it makes sense in some cases to test systems for the risk of Denial of Service (DoS) type attacks. In some cases, a hacker is looking to create any form of negative impact on a target, including taking down critical systems. Real hackers don’t follow the rules and are not concerned about interrupting business if it can improve their situation. This is a key feature that separates a real attacker from an authorized Penetration Tester. Typically, a Penetration Testing exercise is focused on identifying the gaps in security rather than harming a system. ![]()
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