July 12, 2013

Cairo Dock is an OS X like approach to alternative desktop environment. This tutorial will teach you how to install the latest version.

installation :

The Easy Way

In Precise, open your Update Manager. Then, click Settings. Under theOther Software tab, click Add. Paste the following line into the box and enter your password when prompted.
Check for Updates.
Now you need to run just one line in the Terminal.


In the Terminal

Press Ctrl+Alt+T to Open the Terminal :
Installing via the terminal is rather easy.

























Posted on Friday, July 12, 2013 by Unknown

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Sometimes you may be asked if you want to download i386 or amd64. These stand for 32bit and 64bit respectively, and no longer have any relation to your CPU manufacturer (Intel or AMD). This is a simple guide to determining your architecture in a few simple clicks.
First you need to open System Settings. This can be done either in the dash, or by going to the gear icon (top right). From there you need to open System Info.Or Details .

Under the Ubuntu Logo and Version Number, a line will list: OS type     64-bit.
In this example, 64-bit is installed.
32-bit is the only other architecture available.

Posted on Friday, July 12, 2013 by Unknown

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July 10, 2013

If you're new to the Terminal, Pasting Commands probably seems like a godsend. Until it doesn't work. Here's how to do it properly.

Cutting, Copying and Pasting:

This is actually very simple to do.
In most applications Cut, Copy and Paste are Ctrl + XCtrl + C and Ctrl+V respectively.
In the Terminal, Ctrl+C is Cancel Command. The others do things to, but that's not important.
To paste (probably the one you'll use the most), use Ctrl + Shift + V.
Use X or C appropriately for cutting and copying.

Congratulations, you have just learnt how to Cut, Copy, and Paste in the Terminal in Ubuntu!

Posted on Wednesday, July 10, 2013 by Unknown

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An .iso file is an image of a CD, DVD, or BluRay disc. It is a way of storing files in a computer as if they were on a disc. Unfortunately, individual files are not accessible easily, but can be extracted like a zip archive.

Choosing a Disc

Choosing the right disc to write an .iso to isn't all that difficult. First, select your .iso and on the bottom left read how big it is. Now, you simply need to use a disc big enough to fit it on to. CDs are typically 700MB to 1.4GB, DVDs 4.7GB to 9.4GB, and BluRay Discs 25GB to 50GB (all three come in single or dual layer). Your computer also needs a disc drive (optical drive) capable of writing to your chosen disc. DVD Writer drives are fairly commonplace, as are Writeable DVDs.

R or RW

R stands for Recordable, and RW for ReWriteable.
R discs can only be written to once. Once the data is there, it stays there, sort of. It's actually possible to erase them afterwards, but then that's it, you have a permanently blank disc. RW discs can be written to thousands of time. Generally the disc will become to scratched from human handling before it wears out.
As R and RW discs cost roughly the same amount, i would recommend RW.

+ or -

The - (minus) was originally just a hyphen. but was changed (sort of) to be a minus (see what i mean) when the + (plus) discs were introduced.
Plus discs usually cost slightly more, as they support direct writing from a computer, whereas Minus discs require the files to be packaged into an .iso before writing. Seeing as we're burning an .iso, it actually doesn't matter, but Plus discs will be more flexible if your using them later.

Using Brasero

You can Install Brasero from Ubuntu Software center 
Either double-click, or right-click and Write to Disc, and Brasero should open (unless you've installed another image burner). The file is already selected in the top box. Click the bottom box and select the disc you want to write to (if you haven't inserted it yet, now would be a good time). Click Burn. Brasero will write the image to the disc. Wait for it to finish.



Posted on Wednesday, July 10, 2013 by Unknown

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WPScan is a black box WordPress vulnerability scanner.Step 1 :

To install wpscan and her related packages.

sudo apt-get install git libcurl4-gnutls-dev libruby libxml2 libxml2-dev libxslt1-dev ruby1.9.1-dev

sudo -sH
cd /opt
git clone https://github.com/wpscanteam/wpscan.git

cd wpscan

sudo gem install bundler

sudo bundle install --without test developement


Step 2 :

To run it.

sudo -sH
cd /opt/wpscan

./wpscan.rb --url http://www.samiux.com


Step 3 :

To update it.

sudo -sH
cd /opt/wpscan

./wpscan.rb --update

Posted on Wednesday, July 10, 2013 by Unknown

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H i, Today i will show you how to install Skype in Ubuntu 12.04 LTS .


First , you have to download skype from the offcial site
From this link Download Skype for Linux

PS. Click Skip AD to go to the download page .


2- Choose your version ( me i will choose Ubuntu 12.04 (multiarch) )

3-now , once the download has finished , Double click on the downloaded package 

And it the Ubuntu Software center will do the work for you


If you like this Post , Share it .

and if you have any problems contact me

yacine.dz.01@outlook.com or yacine.dz.01@gmail.com

Posted on Wednesday, July 10, 2013 by Unknown

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Applications for Ubuntu/Linux are not at all in short supply. But picking the best from the rest is not an easy thing to do. There are a number of really good bit torrent clients for Ubuntu out there. Here we intend feature a collection of 5 really good bit torrent clients for Ubuntu which we think are among the best.

1-Deluge Bit Torrent Client
  Deluge is among my favorite bit torrent clients for Ubuntu. It is fast, slick and packed with all sorts of functionalities. Deluge is not available in Ubuntu by default, but its in the repositories.


Or you can install From the Terminal

open your Terminal and type this commands
sudo add-apt-repository ppa:deluge-team/ppa
sudo apt-get update 
sudo apt-get install deluge

2-Transmission Bit Torrent Client

 As you all should know already, Transmission is the default bit torrent client in Ubuntu for a long time now. Transmission is a nice mix of simplicity and functionality. And it is my second favorite bit torrent client(after Deluge). It incorporates all the basic features you would expect from a torrent client.

  •  Transmission is available by default in Ubuntu


3_qBittorrent Bit Torrent Client
The qBittorrent project aims to provide a Free Software alternative to µtorrent. Additionally, qBittorrent runs and provides the same features on all major platforms including Linux, Mac OS X and Windows. Like the ones we featured before, qBittorrent is also available in Ubuntu repositories by default.
 




Now, if you want to install the latest bleeding edge(and unstable) version of qBittorrent instead, you need to do the following in Terminal.
sudo add-apt-repository ppa:hydr0g3n/qbittorrent-unstable
sudo apt-get update
sudo apt-get install qbittorrent


4_KTorrent Bit Torrent Client
This is not really a tailor made bit torrent client for Ubuntu GNOME. KTorrent is a KDE application and it looks complete out of place in a GNOME desktop. But apart from that, from a functionality point of view, KTorrent is a more than adequate torrent client of Ubuntu.
 
  • You can install latest version under development version of KTorrent instead via Kubuntu backports PPA(though I haven't tried it myself). 

sudo add-apt-repository ppa:kubuntu-ppa/backports
sudo apt-get update
sudo apt-get install ktorrent

 5_Vuze Bit Torrent Client
Vuze bit torrent client is also a widely used alternative among Ubuntu users. Though I have never really preferred it over the likes of Deluge or Transmission, I have noticed elsewhere that a lot of Linux users actually prefer Vuze(previously called Azureus).

 Click Here to Install Vuze in Ubuntu from official Ubuntu repositories.

I hope that this helped you 





Posted on Wednesday, July 10, 2013 by Unknown

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July 9, 2013

Hi , Today I'll show you  How To securely Remove ubuntu from your computer if it is installed side by side with Windows 7/Vista or XP ( Dual boot )

Most Users remove ubuntu by just deleting the partition where Ubuntu is installed , but by doing that you are affecting the  computer's Boot , because when you delete the partition where Ubuntu is installed , you delete the Boot loader Too . So by doing that you won't be able to access to your Windows 7

Now i'll show how to do that without affecting your boot

1-First you have to Download a Program called  EaseUS Partition Master Free Edition From this link
Download EaseUS-Partition-Master-Free-Edition ( MediaFire link )

PS. : Do Not Download the latest version , because , i didn't found the option that we need
which is " Rebuild MBR " , So , download the version that i have uploaded for you .

Once your download has finished,Install it ( all of you know how to install a program )

after installing the program , Open It . By double clicking on the desktop icon.

Now choose Disk 1 then click on " Rebuild MBR "








Now choose your Windows version , that you are working on right now . Windows 7/XP or Vista ( this an important step )

After choosing your OS , click on OK.
Then click on Apply.


Now Delete the partition where Linux is Installed .

After clicking on Delete  Partition
Click on Apply . And the partitions will be deleted 


Now the Last Step is To Reboot your Computer 
And it'll Boot without Problems 



Finally if you like This Post , Share it with your friends.


If you have any problems , Contact Me At
yacine.dz.01@outlook.com Or yacine.dz.01@gmail.com

Posted on Tuesday, July 09, 2013 by Unknown

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Hi guys , Today i'll show how to download and install the Latest version of .NET framework whis is required to run most of the new programs

The .NET Framework (pronounced dot net) is a software framework developed by Microsoft that runs primarily on Microsoft Windows. It includes a large library and provides language interoperability (each language can use code written in other languages) across several programming languages. Programs written for the .NET Framework execute in a software environment (as contrasted to hardware environment), known as the Common Language Runtime (CLR), an application virtual machine that provides services such as security, memory management, and exception handling. The class library and the CLR together constitute the .NET Framework.
    ( From WikiPedia )

If you want more informations about .NET Framework visit this link :
.NET Framework

Now , It's Time to download :
Download the program (.NET framework ) from the official website here : Download Microsoft .NET Framework 4 Client Profile (Standalone Installer)

Once your download has finished
Follow this pictures to install it.

1- Double click on the icon






2_ do like in the pic. and hit " Install"
















3_ Wait for the verification of file's security.

 4_ Now it's installing , wait a few seconds.

5_Now the installaion has been finished , Click on finish 

Posted on Tuesday, July 09, 2013 by Unknown

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June 22, 2013

اليوم سنرى كيفية ايجاد(انشاء) الدورك (Dork)

كل شيء بالفيديو ، بعد مشاهدة هذا الفيديو ستصير قادر على ايجاد دورك لاي ثغرة 


Posted on Saturday, June 22, 2013 by Unknown

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April 2, 2013

In computing, a denial-of-service attack (DoS attack) or distributed denial-of-service attack (DDoS attack) is an attempt to make a machine or network resource unavailable to its intended users. Although the means to carry out, motives for, and targets of a DoS attack may vary, it generally consists of the efforts of one or more people to temporarily or indefinitely interrupt or suspend services of a host connected to the Internet.
Perpetrators of DoS attacks typically target sites or services hosted on high-profile web servers such as banks, credit card payment gateways, and even root nameservers. This technique has now seen extensive use in certain games, used by server owners, or disgruntled competitors on games such as Minecraft and League of Legends. The term is generally used relating to computer networks, but is not limited to this field; for example, it is also used in reference to CPU resource management.[1]
One common method of attack involves saturating the target machine with external communications requests, so much so that it cannot respond to legitimate traffic, or responds so slowly as to be rendered essentially unavailable. Such attacks usually lead to a server overload. In general terms, DoS attacks are implemented by either forcing the targeted computer(s) to reset, or consuming its resources so that it can no longer provide its intended service or obstructing the communication media between the intended users and the victim so that they can no longer communicate adequately.
Denial-of-service attacks are considered violations of the IAB's Internet proper use policy, and also violate the acceptable use policies of virtually all Internet service providers. They also commonly constitute violations of the laws of individual nations.

Symptoms and manifestations

The United States Computer Emergency Readiness Team (US-CERT) defines symptoms of denial-of-service attacks to include:
  • Unusually slow network performance (opening files or accessing web sites)
  • Unavailability of a particular web site
  • Inability to access any web site
  • Dramatic increase in the number of spam emails received—(this type of DoS attack is considered an e-mail bomb)[2]
  • Disconnection of a wireless or wired internet connection
  • The term "hit offline" being used on you, then you (the target) may disconnect from the internet
Denial-of-service attacks can also lead to problems in the network 'branches' around the actual computer being attacked. For example, the bandwidth of a router between the Internet and a LAN may be consumed by an attack, compromising not only the intended computer, but also the entire network.
If the attack is conducted on a sufficiently large scale, entire geographical regions of Internet connectivity can be compromised without the attacker's knowledge or intent by incorrectly configured or flimsy network infrastructure equipment.

Methods of attack

A "denial-of-service" attack is characterized by an explicit attempt by attackers to prevent legitimate users of a service from using that service. There are two general forms of DoS attacks: those that crash services and those that flood services.
A DoS attack can be perpetrated in a number of ways. The five basic types of attack are:
  1. Consumption of computational resources, such as bandwidth, disk space, or processor time.
  2. Disruption of configuration information, such as routing information.
  3. Disruption of state information, such as unsolicited resetting of TCP sessions.
  4. Disruption of physical network components.
  5. Obstructing the communication media between the intended users and the victim so that they can no longer communicate adequately.
A DoS attack may include execution of malware intended to
  • Max out the processor's usage, preventing any work from occurring.
  • Trigger errors in the microcode of the machine.
  • Trigger errors in the sequencing of instructions, so as to force the computer into an unstable state or lock-up.
  • Exploit errors in the operating system, causing resource starvation and/or thrashing, i.e. to use up all available facilities so no real work can be accomplished or it can crash the system itself
  • Crash the operating system itself.

ICMP flood

A smurf attack is one particular variant of a flooding DoS attack on the public Internet. It relies on misconfigured network devices that allow packets to be sent to all computer hosts on a particular network via the broadcast address of the network, rather than a specific machine. The network then serves as a smurf amplifier. In such an attack, the perpetrators will send large numbers of IP packets with the source address faked to appear to be the address of the victim. The network's bandwidth is quickly used up, preventing legitimate packets from getting through to their destination.[3] To combat Denial of Service attacks on the Internet, services like the Smurf Amplifier Registry have given network service providers the ability to identify misconfigured networks and to take appropriate action such as filtering.
Ping flood is based on sending the victim an overwhelming number of ping packets, usually using the "ping" command from unix-like hosts (the -t flag on Windows systems is much less capable of overwhelming a target, also the -l (size) flag does not allow sent packet size greater than 65500 in Windows). It is very simple to launch, the primary requirement being access to greater bandwidth than the victim.
Ping of death is based on sending the victim a malformed ping packet, which might lead to a system crash.

(S)SYN flood

A SYN flood occurs when a host sends a flood of TCP/SYN packets, often with a forged sender address. Each of these packets is handled like a connection request, causing the server to spawn a half-open connection, by sending back a TCP/SYN-ACK packet (Acknowledge), and waiting for a packet in response from the sender address (response to the ACK Packet). However, because the sender address is forged, the response never comes. These half-open connections saturate the number of available connections the server is able to make, keeping it from responding to legitimate requests until after the attack ends.[4]

Teardrop attacks

A Teardrop attack involves sending mangled IP fragments with overlapping, over-sized payloads to the target machine. This can crash various operating systems because of a bug in their TCP/IP fragmentation re-assembly code.[5] Windows 3.1x, Windows 95 and Windows NT operating systems, as well as versions of Linux prior to versions 2.0.32 and 2.1.63 are vulnerable to this attack.
Around September 2009, a vulnerability in Windows Vista was referred to as a "teardrop attack", but the attack targeted SMB2 which is a higher layer than the TCP packets that teardrop used.[6][7]

Low-rate Denial-of-Service attacks

The Low-rate DoS (LDoS) attack exploits TCP’s slow-time-scale dynamics of retransmission time-out (RTO) mechanisms to reduce TCP throughput. Basically, an attacker can cause a TCP flow to repeatedly enter a RTO state by sending high-rate, but short-duration bursts, and repeating periodically at slower RTO time-scales. The TCP throughput at the attacked node will be significantly reduced while the attacker will have low average rate making it difficult to be detected.[8]

Peer-to-peer attacks

Attackers have found a way to exploit a number of bugs in peer-to-peer servers to initiate DDoS attacks. The most aggressive of these peer-to-peer-DDoS attacks exploits DC++. Peer-to-peer attacks are different from regular botnet-based attacks. With peer-to-peer there is no botnet and the attacker does not have to communicate with the clients it subverts. Instead, the attacker acts as a "puppet master," instructing clients of large peer-to-peer file sharing hubs to disconnect from their peer-to-peer network and to connect to the victim's website instead. As a result, several thousand computers may aggressively try to connect to a target website. While a typical web server can handle a few hundred connections per second before performance begins to degrade, most web servers fail almost instantly under five or six thousand connections per second. With a moderately large peer-to-peer attack, a site could potentially be hit with up to 750,000 connections in short order. The targeted web server will be plugged up by the incoming connections.
While peer-to-peer attacks are easy to identify with signatures, the large number of IP addresses that need to be blocked (often over 250,000 during the course of a large-scale attack) means that this type of attack can overwhelm mitigation defenses. Even if a mitigation device can keep blocking IP addresses, there are other problems to consider. For instance, there is a brief moment where the connection is opened on the server side before the signature itself comes through. Only once the connection is opened to the server can the identifying signature be sent and detected, and the connection torn down. Even tearing down connections takes server resources and can harm the server.
This method of attack can be prevented by specifying in the peer-to-peer protocol which ports are allowed or not. If port 80 is not allowed, the possibilities for attack on websites can be very limited.

Asymmetry of resource utilization in starvation attacks

An attack which is successful in consuming resources on the victim computer must be either:
  • carried out by an attacker with great resources, by either:
    • controlling a computer with great computation power or, more commonly, large network bandwidth
    • controlling a large number of computers and directing them to attack as a group. A DDOS attack is the primary example of this.
  • taking advantage of a property of the operating system or applications on the victim system which enables an attack consuming vastly more of the victim's resources than the attacker's (an asymmetric attack). Smurf attack, SYN flood, Sockstress and NAPTHA are all asymmetric attacks.
An attack may utilize a combination of these methods in order to magnify its power.

Permanent denial-of-service attacks

A permanent denial-of-service (PDoS), also known loosely as flashing,[9] is an attack that damages a system so badly that it requires replacement or reinstallation of hardware.[10] Unlike the distributed denial-of-service attack, a PDoS attack exploits security flaws which allow remote administration on the management interfaces of the victim's hardware, such as routers, printers, or other networking hardware. The attacker uses these vulnerabilities to replace a device's firmware with a modified, corrupt, or defective firmware image—a process which when done legitimately is known as flashing. This therefore "bricks" the device, rendering it unusable for its original purpose until it can be repaired or replaced.
The PDoS is a pure hardware targeted attack which can be much faster and requires fewer resources than using a botnet in a DDoS attack. Because of these features, and the potential and high probability of security exploits on Network Enabled Embedded Devices (NEEDs), this technique has come to the attention of numerous hacker communities. PhlashDance is a tool created by Rich Smith (an employee of Hewlett-Packard's Systems Security Lab) used to detect and demonstrate PDoS vulnerabilities at the 2008 EUSecWest Applied Security Conference in London.[11]

Application-level floods

Various DoS-causing exploits such as buffer overflow can cause server-running software to get confused and fill the disk space or consume all available memory or CPU time.
Other kinds of DoS rely primarily on brute force, flooding the target with an overwhelming flux of packets, oversaturating its connection bandwidth or depleting the target's system resources. Bandwidth-saturating floods rely on the attacker having higher bandwidth available than the victim; a common way of achieving this today is via Distributed Denial of Service, employing a botnet. Other floods may use specific packet types or connection requests to saturate finite resources by, for example, occupying the maximum number of open connections or filling the victim's disk space with logs.
A "banana attack" is another particular type of DoS. It involves redirecting outgoing messages from the client back onto the client, preventing outside access, as well as flooding the client with the sent packets.
An attacker with shell-level access to a victim's computer may slow it until it is unusable or crash it by using a fork bomb.
A kind of application-level DoS attack is XDoS (or XML DoS) which can be controlled by modern Web Application Firewalls (WAFs).

Nuke

A Nuke is an old denial-of-service attack against computer networks consisting of fragmented or otherwise invalid ICMP packets sent to the target, achieved by using a modified ping utility to repeatedly send this corrupt data, thus slowing down the affected computer until it comes to a complete stop.
A specific example of a nuke attack that gained some prominence is the WinNuke, which exploited the vulnerability in the NetBIOS handler in Windows 95. A string of out-of-band data was sent to TCP port 139 of the victim's machine, causing it to lock up and display a Blue Screen of Death (BSOD).

R-U-Dead-Yet? (RUDY)

This attack is one of many web application DoS tools available to directly attack web applications by starvation of available sessions on the web server. Much like Slowloris, RUDY keeps sessions at halt using never-ending POST transmissions and sending an arbitrarily large content-length header value.

Slow Read attack

Slow Read attack sends legitimate application layer requests but reads responses very slowly, thus trying to exhaust the server's connection pool. Slow reading is achieved by advertising very small number for the TCP Receive Window size and at the same time by emptying clients' TCP receive buffer slowly. That naturally ensures a very low data flow rate.

Distributed attack

A distributed denial of service attack (DDoS) occurs when multiple systems flood the bandwidth or resources of a targeted system, usually one or more web servers. This is the result of multiple compromised systems (for example a botnet) flooding the targeted system(s) with traffic. When a server is overloaded with connections, new connections can no longer be accepted.
Malware can carry DDoS attack mechanisms; one of the better-known examples of this was MyDoom. Its DoS mechanism was triggered on a specific date and time. This type of DDoS involved hardcoding the target IP address prior to release of the malware and no further interaction was necessary to launch the attack.
A system may also be compromised with a trojan, allowing the attacker to download a zombie agent (or the trojan may contain one). Attackers can also break into systems using automated tools that exploit flaws in programs that listen for connections from remote hosts. This scenario primarily concerns systems acting as servers on the web.
Stacheldraht is a classic example of a DDoS tool. It utilizes a layered structure where the attacker uses a client program to connect to handlers, which are compromised systems that issue commands to the zombie agents, which in turn facilitate the DDoS attack. Agents are compromised via the handlers by the attacker, using automated routines to exploit vulnerabilities in programs that accept remote connections running on the targeted remote hosts. Each handler can control up to a thousand agents.[12]
These collections of systems compromisers are known as botnets. DDoS tools like Stacheldraht still use classic DoS attack methods centered on IP spoofing and amplification like smurf attacks and fraggle attacks (these are also known as bandwidth consumption attacks). SYN floods (also known as resource starvation attacks) may also be used. Newer tools can use DNS servers for DoS purposes. See next section.
Simple attacks such as SYN floods may appear with a wide range of source IP addresses, giving the appearance of a well distributed DoS. These flood attacks do not require completion of the TCP three way handshake and attempt to exhaust the destination SYN queue or the server bandwidth. Because the source IP addresses can be trivially spoofed, an attack could come from a limited set of sources, or may even originate from a single host. Stack enhancements such as syn cookies may be effective mitigation against SYN queue flooding, however complete bandwidth exhaustion may require involvement.
Unlike MyDoom's DDoS mechanism, botnets can be turned against any IP address. Script kiddies use them to deny the availability of well known websites to legitimate users.[13] More sophisticated attackers use DDoS tools for the purposes of extortion – even against their business rivals.[14]
If an attacker mounts an attack from a single host it would be classified as a DoS attack. In fact, any attack against availability would be classed as a Denial of Service attack. On the other hand, if an attacker uses many systems to simultaneously launch attacks against a remote host, this would be classified as a DDoS attack.
The major advantages to an attacker of using a distributed denial-of-service attack are that: multiple machines can generate more attack traffic than one machine, multiple attack machines are harder to turn off than one attack machine, and that the behavior of each attack machine can be stealthier, making it harder to track and shut down. These attacker advantages cause challenges for defense mechanisms. For example, merely purchasing more incoming bandwidth than the current volume of the attack might not help, because the attacker might be able to simply add more attack machines.
In some cases a machine may become part of a DDoS attack with the owner's consent. An example of this is the 2010 DDoS attack against major credit card companies by supporters of WikiLeaks. In cases such as this, supporters of a movement (in this case, those opposing the arrest of WikiLeaks founder Julian Assange) choose to download and run DDoS software.

Reflected / Spoofed attack

A distributed reflected denial of service attack (DRDoS) involves sending forged requests of some type to a very large number of computers that will reply to the requests. Using Internet Protocol address spoofing, the source address is set to that of the targeted victim, which means all the replies will go to (and flood) the target.
ICMP Echo Request attacks (Smurf Attack) can be considered one form of reflected attack, as the flooding host(s) send Echo Requests to the broadcast addresses of mis-configured networks, thereby enticing many hosts to send Echo Reply packets to the victim. Some early DDoS programs implemented a distributed form of this attack.
Many services can be exploited to act as reflectors, some harder to block than others.[15] DNS amplification attacks involve a new mechanism that increased the amplification effect, using a much larger list of DNS servers than seen earlier.[16]

Unintentional denial of service

This describes a situation where a website ends up denied, not due to a deliberate attack by a single individual or group of individuals, but simply due to a sudden enormous spike in popularity. This can happen when an extremely popular website posts a prominent link to a second, less well-prepared site, for example, as part of a news story. The result is that a significant proportion of the primary site's regular users – potentially hundreds of thousands of people – click that link in the space of a few hours, having the same effect on the target website as a DDoS attack. A VIPDoS is the same, but specifically when the link was posted by a celebrity.
When Michael Jackson died in 2009, websites such as Google and Twitter slowed down or even crashed.[17] Many sites' servers thought the requests were from a virus or spyware trying to cause a Denial of Service attack, warning users that their queries looked like "automated requests from a computer virus or spyware application".[18]
News sites and link sites – sites whose primary function is to provide links to interesting content elsewhere on the Internet – are most likely to cause this phenomenon. The canonical example is the Slashdot effect when receiving traffic from Slashdot. Sites such as Reddit, Digg, the Drudge Report, Fark, Something Awful, and the webcomic Penny Arcade have their own corresponding "effects", known as "the Digg effect", being "drudged", "farking", "goonrushing" and "wanging"; respectively.
Routers have also been known to create unintentional DoS attacks, as both D-Link and Netgear routers have created NTP vandalism by flooding NTP servers without respecting the restrictions of client types or geographical limitations.
Similar unintentional denials of service can also occur via other media, e.g. when a URL is mentioned on television. If a server is being indexed by Google or another search engine during peak periods of activity, or does not have a lot of available bandwidth while being indexed, it can also experience the effects of a DoS attack.
Legal action has been taken in at least one such case. In 2006, Universal Tube & Rollform Equipment Corporation sued YouTube: massive numbers of would-be youtube.com users accidentally typed the tube company's URL, utube.com. As a result, the tube company ended up having to spend large amounts of money on upgrading their bandwidth.[19]

Denial-of-Service Level II

The goal of DoS L2 (possibly DDoS) attack is to cause a launching of a defense mechanism which blocks the network segment from which the attack originated. In case of distributed attack or IP header modification (that depends on the kind of security behavior) it will fully block the attacked network from Internet, but without system crash.

Performing DoS-attacks

A wide array of programs are used to launch DoS-attacks. Most of these programs are completely focused on performing DoS-attacks, while others are also true Packet injectors, thus able to perform other tasks as well. Such tools are intended for benign use, but they can also be utilized in launching attacks on victim networks.

Prevention and response

Defending against Denial of Service attacks typically involves the use of a combination of attack detection, traffic classification and response tools, aiming to block traffic that they identify as illegitimate and allow traffic that they identify as legitimate.[20] A list of prevention and response tools is provided below:

Firewalls

Firewalls can be set up to have simple rules such to allow or deny protocols, ports or IP addresses. In the case of a simple attack coming from a small number of unusual IP addresses for instance, one could put up a simple rule to drop all incoming traffic from those attackers.
More complex attacks will however be hard to block with simple rules: for example, if there is an ongoing attack on port 80 (web service), it is not possible to drop all incoming traffic on this port because doing so will prevent the server from serving legitimate traffic.[21] Additionally, firewalls may be too deep in the network hierarchy. Routers may be affected before the traffic gets to the firewall. Nonetheless, firewalls can effectively prevent users from launching simple flooding type attacks from machines behind the firewall.
Some stateful firewalls, like OpenBSD's pf(4) packet filter, can act as a proxy for connections: the handshake is validated (with the client) instead of simply forwarding the packet to the destination. It is available for other BSDs as well. In that context, it is called "synproxy".

Switches

Most switches have some rate-limiting and ACL capability. Some switches provide automatic and/or system-wide rate limiting, traffic shaping, delayed binding (TCP splicing), deep packet inspection and Bogon filtering (bogus IP filtering) to detect and remediate denial of service attacks through automatic rate filtering and WAN Link failover and balancing.[citation needed]
These schemes will work as long as the DoS attacks are something that can be prevented by using them. For example SYN flood can be prevented using delayed binding or TCP splicing. Similarly content based DoS may be prevented using deep packet inspection. Attacks originating from dark addresses or going to dark addresses can be prevented using Bogon filtering. Automatic rate filtering can work as long as you have set rate-thresholds correctly and granularly. Wan-link failover will work as long as both links have DoS/DDoS prevention mechanism.[citation needed]

Routers

Similar to switches, routers have some rate-limiting and ACL capability. They, too, are manually set. Most routers can be easily overwhelmed under DoS attack. Cisco IOS has features that prevent flooding, i.e. example settings.[22]

Application front end hardware

Application front end hardware is intelligent hardware placed on the network before traffic reaches the servers. It can be used on networks in conjunction with routers and switches. Application front end hardware analyzes data packets as they enter the system, and then identifies them as priority, regular, or dangerous. There are more than 25 bandwidth management vendors.

IPS based prevention

Intrusion-prevention systems (IPS) are effective if the attacks have signatures associated with them. However, the trend among the attacks is to have legitimate content but bad intent. Intrusion-prevention systems which work on content recognition cannot block behavior-based DoS attacks.
An ASIC based IPS may detect and block denial of service attacks because they have the processing power and the granularity to analyze the attacks and act like a circuit breaker in an automated way.[citation needed]
A rate-based IPS (RBIPS) must analyze traffic granularly and continuously monitor the traffic pattern and determine if there is traffic anomaly. It must let the legitimate traffic flow while blocking the DoS attack traffic.

DDS based defense

More focused on the problem than IPS, a DoS Defense System (DDS) is able to block connection-based DoS attacks and those with legitimate content but bad intent. A DDS can also address both protocol attacks (such as Teardrop and Ping of death) and rate-based attacks (such as ICMP floods and SYN floods).
Like IPS, a purpose-built system, such as the well-known Corero DDS products, can detect and block denial of service attacks at much nearer line speed than a software based system.

Blackholing and sinkholing

With blackholing, all the traffic to the attacked DNS or IP address is sent to a "black hole" (null interface, non-existent server, ...). To be more efficient and avoid affecting network connectivity, it can be managed by the ISP.[23]
Sinkholing routes to a valid IP address which analyzes traffic and rejects bad ones. Sinkholing is not efficient for most severe attacks.

Clean pipes

All traffic is passed through a "cleaning center" or a "scrubbing center" via various methods such as proxies, tunnels or even direct circuits, which separates "bad" traffic (DDoS and also other common internet attacks) and only sends good traffic beyond to the server. The provider needs central connectivity to the Internet to manage this kind of service unless they happen to be located within the same facility as the "cleaning center" or "scrubbing center".[24]
Prolexic, Tata Communications and Verisign are examples of providers of this service.[25][26]

Side effects of DoS attacks

Backscatter

In computer network security, backscatter is a side-effect of a spoofed denial-of-service attack. In this kind of attack, the attacker spoofs (or forges) the source address in IP packets sent to the victim. In general, the victim machine cannot distinguish between the spoofed packets and legitimate packets, so the victim responds to the spoofed packets as it normally would. These response packets are known as backscatter.[27]
If the attacker is spoofing source addresses randomly, the backscatter response packets from the victim will be sent back to random destinations. This effect can be used by network telescopes as indirect evidence of such attacks.
The term "backscatter analysis" refers to observing backscatter packets arriving at a statistically significant portion of the IP address space to determine characteristics of DoS attacks and victims.

Posted on Tuesday, April 02, 2013 by Unknown

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