all about DDoS Attack

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

See also: Smurf attack, Ping flood, and Ping of death

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.

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How the Spamhaus DDoS attack could have been prevented

Nearly 13 years ago, the wizardly band of engineers who invented and continue to defend the Internet published a prescient document they called BCP38, which described ways to thwart the most common forms of distributed denial-of-service attack.
BCP38, short for Best Current Practice #38, was published soon after debilitating denial of service attacks crippled eBay, Amazon, Yahoo, and other major sites in February 2000. If those guidelines to stop malcontents from forging Internet addresses had been widely adopted by the companies, universities, and government agencies that operate the modern Internet, this week's electronic onslaught targeting Spamhaus would have been prevented.
But they weren't. So a 300-gigabit-per-second torrent of traffic flooded into the networks of companies including Spamhaus, Cloudflare, and key Internet switching stations in Amsterdam, Frankfurt, and London. It was like 1,000 cars trying to crowd onto a highway designed for 100 vehicles at a time. Cloudflare dubbed it, perhaps a bit too dramatically, the attack "that almost broke the Internet."
BCP38 outlined how providers can detect and then ignore the kind of forged Internet addresses that were used in this week's DDoS attack. Since its publication, though, adoption has been haphazard. Hardware generally needs to be upgraded. Employees and customers need to be trained. Routers definitely need to be reconfigured. The cost for most providers, in other words, has exceeded the benefits.
"There's an asymmetric cost-benefit here," said Paul Vixie, an engineer and Internet pioneer who serves on the Internet Corporation for Assigned Names and Numbers' security advisory board. That's because, Vixie said, the provider that takes the time to secure its networks makes all the investment, while other providers "get all the reward."
BCP38 is designed to verify that someone claiming to be located in a certain corner of the Internet actually is there. It's a little like a rule that the Postal Service might impose if there's a deluge of junk mail with fake return addresses originating from a particular ZIP code. If you're sending a letter from San Francisco, the new rule might say, your return label needs to sport a valid northern California address, not one falsely purporting to originate in Hong Kong or Paris. It might annoy the occasional tourist, but it would probably work in most cases.
This week's anti-Spamhaus onslaught relied on attackers spoofing Internet addresses, then exploiting a feature of the domain name system (DNS) called open recursors or open recursive resolvers. Because of a quirk in the design of one of the Internet's workhorse protocols, these can amplify traffic over 30 times and overwhelm all but the best-defended targets.
The countermeasures
Preventing spoofing through BCP38 will prevent this type of amplification attack. "There is no way to exploit DNS servers of any type, including open recursors, to attack any third party without the ability to spoof traffic," said Arbor Networks' Roland Dobbins. "The ability to spoof traffic is what makes the attack possible. Take away the ability to spoof traffic, and DNS servers may no longer be abused to send floods of traffic to DDoS third parties."
Other countermeasures exist. One of them is to lock down open recursive resolvers by allowing them to be used only by authorized users. There are about 27 million DNS resolvers on the global Internet. Of those, a full 25 million "pose a significant threat" and need to be reconfigured, according to a survey conducted by the Open Resolver Project. Reprogramming them all is the very definition of a non-trivial task.
"You could stop this attack in either of two ways," said Matthew Prince, co-founder and CEO of CloudFlare, which helped defend against this week's attack. "One, shut down the open resolvers, or two, get all the networks to implement BCP38. The attackers need both in order to generate this volume of attack traffic."

Alternatively, networks don't need to lock down open resolvers completely. Google, which operates one of the world's largest networks, has adopted an innovative rate-limiting technique. It describes rate-limiting as a way to "protect any other systems against amplification and traditional distributed DoS (botnet) attacks that could be launched from our resolver servers."
But few companies, universities, individuals, and assorted network operators are going to be as security-conscious as Mountain View's teams of very savvy engineers. Worse yet, even if open recursive resolvers are closed to the public, attackers can switch to other services that rely on UDP, the Internet's User Datagram Protocol. Network management protocols and time-synchronization protocols -- all designed for a simpler, more innocent era -- can also be pressed into service as destructive traffic reflectors.
The reflection ratios may not be as high as 1:30, but they're still enough to interest someone with malicious intent. Arbor Networks has spotted attacks based on traffic amplification from SNMP, a network management protocol, that exceed 30 gigabits per second. Closing open DNS resolvers won't affect attacks that use SNMP to club unwitting targets.
Which is, perhaps, the best argument for BCP38. The most common way to curb spoofing under BCP38 is with a technique called Unicast Reverse Path Forwarding (uRPF) to try to weed out unwanted traffic. But that needs to be extended to nearly every customer of a provider or network operator, a daunting undertaking.
Nick Hilliard, chief technology officer for INEX, an Internet exchange based in Dublin, Ireland, said:

BCP38 is harder than it looks because in order to implement it properly, you need to roll out uRPF or interface [access control lists] to every single customer edge point on the internet. I.e. every DSL link, every cable modem, every VPS in a provider's cloud hosting centre and so forth. The scale of this undertaking is huge: there is lots of older (and sometimes new) equipment in production out there which either doesn't support uRPF (in which case you can usually write access filters to compensate), or which supports uRPF but badly (i.e. the kit might support it for IPv4 but not IPv6). If you're a network operator and you can't use uRPF because your kit won't support it, installing and maintaining individual access filtering on your customer edge is impossible without good automated tools to do so, and many service providers don't have these.

Translation: It all adds up to being really hard.
Vixie, who wrote an easy-to-read description of the problem back in 2002, suggested it's a little like fire, building, and safety codes: the government "usually takes a role" forcing everyone to adopt the same standards, and roughly the same costs. Eventually, he suggests, nobody complains that their competitors are getting away without paying compliance costs.
That argument crops up frequently enough in technical circles, but it tends to be shot down just as fast. For one thing, wielding a botnet to carry out a DDoS attack is already illegal in the United States and just about everywhere else in the civilized world. And as a practical matter, botnet-managing criminals can change their tactics faster than a phalanx of professional bureaucrats in Washington, D.C. or other national capitals can respond.
INEX's Hilliard said the real answer is to change the economics to make it less profitable to carry out DDoS attacks.
When sending spam was cheap, Hilliard said, he was receiving 10,000 Viagra offers a month. But after network providers took concerted steps to crack down, "the economics changed and so did the people who were abusing the Internet, and now I get about 2,000 a month, all of which end up in my spam folder," he said. "The same thing will happen to DDoS attacks: in 10 years' time, we will have a lot more in terms of BCP38 coverage, and we won't get upset as much about the small but steady stream of 300-gigabit attacks."

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Undersea Network Cables Attacked Near Egypt

Three men arrested off Alexandria accused of trying to cut an undersea cable called Sea-WE-Me-4

Egyptian naval forces have arrested three scuba divers who they say were trying to cut an undersea cable off the port of Alexandria that provides one-third of all internet capacity between Europe and Egypt.
However the navy who captured the men had no explanation of who they were working for, where they came from or why they would want to disrupt Egypt's internet communications.
Pictures on the Egyptian coastguard's Facebook page showed the three men tied up on board a boat, and alleged they were cutting an undersea cable partly owned by Telecom Egypt, the country's main communications organisation. The men had been on a fishing boat, said a statement by Colonel Ahmed Mohammed Ali, but offered no other details.
The world internet submarine cable map by the telecoms analysis company Telegeography shows that six cables come aground at Alexandria. The men were allegedly trying to cut the SeaWeMe-4 (South-east Asia-Middle East-Western Europe-4) cable, able to carry a third of the traffic between Europe and Egypt. Covering a distance of 20,000km, it enters the sea at Marseilles and makes landfall in Annaba in 15 other countries including Sri Lanka, Thailand and India.
 

Map showing the location of Sea-We-Me-4 cable. Source: Telegeography 

 

  It is one of eight undersea cables between Europe and Egypt - so cutting one would not immediately destroy connectivity, but would lead to congestion and slowdowns.
However reports earlier this week suggested cable breaks on four cables around Egypt - IMEWE (linking France to India via Alexandria and Suez), TE-North (owned by Telecom Egypt), EIG (Europe India Gateway), and SEA-ME-WE-3, a partner to the cable that was allegedly attacked. That would cause significant interruptions to internet services.
Internet services in Egypt have been suffering disruption since 22 March, apparently after a ship's anchor cut through another cable.
Worldwide, undersea cables carry 99% of intercontinental internet traffic, and form complex networks across the world. Jim Cowie, co-founder and chief technology officer at the network security company Renesys, said that internet connections had been slowed down as far away as Pakistan and India.
Internet connectivity in the Middle East was seriously affected in 2008 when ships' anchors cut through cables, which cut capacity between Europe and Africa by up to 70%.
Update: this article was corrected on 31 March 2013 to add the phrase "significant interruptions to internet services" at the end of the sixth paragraph, which had been omitted due to an editing error.

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10 Tips for Wireless Home Network Security

Many folks setting up wireless home networks rush through the job to get their Internet connectivity working as quickly as possible. That's totally understandable. It's also quite risky as numerous security problems can result. Today's Wi-Fi networking products don't always help the situation as configuring their security features can be time-consuming and non-intuitive. The recommendations below summarize the steps you should take to improve the security of your home wireless network.

1. Change Default Administrator Passwords (and Usernames)

At the core of most Wi-Fi home networks is an access point or router. To set up these pieces of equipment, manufacturers provide Web pages that allow owners to enter their network address and account information. These Web tools are protected with a login screen (username and password) so that only the rightful owner can do this. However, for any given piece of equipment, the logins provided are simple and very well-known to hackers on the Internet. Change these settings immediately.

2. Turn on (Compatible) WPA / WEP Encryption

All Wi-Fi equipment supports some form of encryption. Encryption technology scrambles messages sent over wireless networks so that they cannot be easily read by humans. Several encryption technologies exist for Wi-Fi today. Naturally you will want to pick the strongest form of encryption that works with your wireless network. However, the way these technologies work, all Wi-Fi devices on your network must share the identical encryption settings. Therefore you may need to find a "lowest common demoninator" setting.

3. Change the Default SSID

Access points and routers all use a network name called the SSID. Manufacturers normally ship their products with the same SSID set. For example, the SSID for Linksys devices is normally "linksys." True, knowing the SSID does not by itself allow your neighbors to break into your network, but it is a start. More importantly, when someone finds a default SSID, they see it is a poorly configured network and are much more likely to attack it. Change the default SSID immediately when configuring wireless security on your network.

4. Enable MAC Address Filtering

Each piece of Wi-Fi gear possesses a unique identifier called the physical address or MAC address. Access points and routers keep track of the MAC addresses of all devices that connect to them. Many such products offer the owner an option to key in the MAC addresses of their home equipment, that restricts the network to only allow connections from those devices. Do this, but also know that the feature is not so powerful as it may seem. Hackers and their software programs can fake MAC addresses easily.

5. Disable SSID Broadcast

In Wi-Fi networking, the wireless access point or router typically broadcasts the network name (SSID) over the air at regular intervals. This feature was designed for businesses and mobile hotspots where Wi-Fi clients may roam in and out of range. In the home, this roaming feature is unnecessary, and it increases the likelihood someone will try to log in to your home network. Fortunately, most Wi-Fi access points allow the SSID broadcast feature to be disabled by the network administrator.

6. Do Not Auto-Connect to Open Wi-Fi Networks

Connecting to an open Wi-Fi network such as a free wireless hotspot or your neighbor's router exposes your computer to security risks. Although not normally enabled, most computers have a setting available allowing these connections to happen automatically without notifying you (the user). This setting should not be enabled except in temporary situations.

7. Assign Static IP Addresses to Devices

Most home networkers gravitate toward using dynamic IP addresses. DHCP technology is indeed easy to set up. Unfortunately, this convenience also works to the advantage of network attackers, who can easily obtain valid IP addresses from your network's DHCP pool. Turn off DHCP on the router or access point, set a fixed IP address range instead, then configure each connected device to match. Use a private IP address range (like 10.0.0.x) to prevent computers from being directly reached from the Internet.

8. Enable Firewalls On Each Computer and the Router

Modern network routers contain built-in firewall capability, but the option also exists to disable them. Ensure that your router's firewall is turned on. For extra protection, consider installing and running personal firewall software on each computer connected to the router.

9. Position the Router or Access Point Safely

Wi-Fi signals normally reach to the exterior of a home. A small amount of signal leakage outdoors is not a problem, but the further this signal reaches, the easier it is for others to detect and exploit. Wi-Fi signals often reach through neighboring homes and into streets, for example. When installing a wireless home network, the position of the access point or router determines its reach. Try to position these devices near the center of the home rather than near windows to minimize leakage.

10. Turn Off the Network During Extended Periods of Non-Use

The ultimate in wireless security measures, shutting down your network will most certainly prevent outside hackers from breaking in! While impractical to turn off and on the devices frequently, at least consider doing so during travel or extended periods offline. Computer disk drives have been known to suffer from power cycle wear-and-tear, but this is a secondary concern for broadband modems and routers.

If you own a wireless router but are only using it wired (Ethernet) connections, you can also sometimes turn off Wi-Fi on a broadband router without powering down the entire network.

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HTML5 Developers network learn from HTML5 developers.

There is a new networking site built specifically for HTML5 developers, designers, programmers, and potential clients requiring HTML5 services.  The unfortunate aspect of the new site is that it does not yet have any members.  Without members, it is impossible to create an ecosystem to help us all learn more about HTML5.  If you have interest in learning or teaching about HTML5, please stop by the new site to create a profile.  Hopefully this will develop into a place of learning.  The site is found at www.HTML5Developers.org

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