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Monday, 5 August 2013

DOS Attack


Denial of Service , if you are unable to hack a website then the last option is to use DOS.
It goes with the name, denial of service, wherein you degrade the services of the server by sending as many packets as possible it causes the target system to crash, reboot, or otherwise deny services to legitimate users.
There are several different kinds of dos attacks as
discussed below:-
1) Ping Of Death :- The ping of death attack sends oversized ICMP datagrams (encapsulated in IP packets) to the victim.The Ping command makes use of the ICMP echo request and echo reply messages and it’s commonly used to determine whether the remote host is alive. In a ping of death attack, however, ping causes the remote system to hang, reboot or crash. To do so the attacker uses, the ping command in conjuction with -l argument (used to specify the size of the packet sent) to ping the target system that exceeds the maximum bytes allowed by TCP/IP (65,536).
example:- c:/>ping -l 65540 hostname
2) Teardrop Attack :- Whenever data is sent over the internet, it is broken into fragments at the source system and reassembled at the destination system. For example you need to send 3,000 bytes of data from one system to another. Rather than sending the entire chunk in asingle packet, the data is broken down into smaller packets as given below:
* packet 1 will carry bytes 1-1000.
* packet 2 will carry bytes 1001-2000.
* packet 3 will carry bytes 2001-3000.
In teardrop attack, however, the data packets sent to the target computer contais bytes that overlaps with each other.
(bytes 1-1500) (bytes 1001-2000) (bytes 1500-2500)
When the target system receives such a series of packets, it can not reassemble the data and therefore will crash, hang, or reboot.
Old Linux systems, Windows NT/95 are vulnerable
3) SYN – Flood Attack :- In SYN flooding attack, several SYN packets are sent to the target host, all with an invalid source IP address. When the target system receives these SYN packets, it tries to respond to each one with a SYN/ACK packet but as all the source IP addresses are invalid the target system goes into wait state for ACK message to receive from source. Eventually, due to large number of connection requests, the target systems’ memory is consumed. In order to actually affect the target system, a large number of SYN packets with invalid IP addresses must be sent.
4)UDP – Flood Attack :- Two UDP services: echo (which echos back any character received) and chargen (which generates character) were used in the past for network testing and are enabled by default on most systems. These services can be used to launch a DOS by connecting the chargen to echo ports on the same or another machine and generating large amounts of network traffic.

Following are the tools which can help you out to perform DOS.

List Of Top 10 DOS Attack Tools :
1.    Jolt2

2.    Bubonic.c

3.    Land and Latierra

4.    Targa

5.    Blast 2 0
7.    Panther 2
8.    Crazy Pinger

9.    Some Trouble
link:-

10.    UDP Flood

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