Amer-networks E5Web GUI Manual de usuario descargar pdf (Pagina 481)

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6.6. Denial-of-Service Attacks

6.6.1. Overview

The same advantages that the Internet brings to business also benefit hackers who use the same

public infrastructure to mount attacks. Attack toolkits are readily available and development

work on these is often split across groups spread around the world. Many newer attack

techniques utilize the distributed topology of the Internet to launch Denial of Service (DoS)

attacks resulting in paralyzed web servers that can no longer respond to legitimate connection

requests.

To be on the receiving end of a DoS attack is probably the last thing any network administrator

wants to experience. Attacks can appear out of thin air and the consequences can be devastating

with crashed servers, jammed Internet connections and business critical systems overloaded.

This section deals with how cOS Core is used to protect against these attacks.

6.6.2. DoS Attack Mechanisms

A DoS attack can be perpetrated in a number of ways but there are three basic types of attack:

• Consumption of computational resources, such as bandwidth, disk space or CPU time.

• Disruption of configuration information, such as routing information.

• Disruption of physical network components.

One of the most commonly used method is the consumption of computational resources which

means that the DoS attack floods the network and ties up critical resources used to run business

critical applications. In some cases, vulnerabilities in the Unix and Windows operating systems

are exploited to intentionally crash the system, while in other cases large amounts of apparently

valid traffic are directed at sites until they become overloaded and crash.

Some of the most well known DoS attacks during the brief history of the public Internet have

included the following:

• Ping of Death attacks

• Fragmentation overlap attacks

• Land and LaTierra attacks

• The WinNuke attack

• Amplification attacks

• TCP SYN flood attacks

6.6.3. Ping of Death Attacks

This is one of the earliest OSI layer 3/4 attacks. A simple ways to execute this is to run the console

command "ping -l 65510 o.p.q.r" on certain operating systems where o.p.q.r is the IP address of

the intended victim. Jolt is the name of one of the purpose-written programs for generating such

packets on operating systems whose ping commands refuse to generate oversized packets.

Another name for this type of attack is Ping of Death.

Chapter 6: Security Mechanisms

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