A Brief on Denial-of-Service attacks

David Moore, Stefan Savage and Geoff Voelker, a University of California, San Diego computing team decided to asess denial-of-service attacks by watching the response messages sent from a victim´s computer, which is called backscatter. The issue of January-February 2002 of Science Observer brings the news.

Moore and his colleagues watched traffic for three one-week periods. Each time, they monitored more than 16 million addresses, which cover 1/256 of all addresses space on the Internet. Said Savage: "In general, I´d say that we´ve demonstrated that denial-of-service attacks are both common and widespread. We have indications that there are several different kinds of attackers who mount attacks with different intensities and likely for different sorts of reasons. These range from individual vendettas that only impact a small number of systems to broader based attacks that pose a substantial threat to large content providers or even moderate-sized service providers."

Now some piracy from http://www.irchelp.org/irchelp/nuke/ :

There are two types of DoS attacks, both of which are described in the next major section:

1. Operating System attacks, which target bugs in specific operating systems and can be fixed with patches.
2. Networking attacks, which exploit inherent limitations of networking and may require firewall protection.

Operating System Attacks
These attacks exploit bugs in a specific operating system (OS), which is the basic software that your computer runs, such as Windows 98 or MacOS. In general, when these problems are identified, they are eventually fixed by the company such as Microsoft. So as a first step, always make sure you have the very latest version of your operating system, including all bug fixes. All Windows users should regularly visit Microsoft's Windows Update Site which automatically checks to see if you need any updates.

Networking Attacks
These attacks exploit inherent limitations of networking to disconnect you from the IRC server or your ISP, but don't usually cause your computer to crash. Sometimes it doesn't even matter what kind of operating system you use, and you cannot patch or fix the problem directly. The attacks on Yahoo and Amazon mentioned at the top of this page were large scale networking attacks, and demonstrate how nobody is safe against a very determined attacker. Network attacks include ICMP flood (ping flood) and smurf which are outright floods of data to overwhelm the finite capacity of your connection, spoofed unreach/redirect aka "click" which tricks your computer into thinking there is a network failure and voluntarily breaking the connection, and a whole new generation of distributed denial of service attacks (although these are seldom used against individuals).
End of Piracy.

In those three weeks they analized more than 12,000 attacks. Most of them sent fewer than 1,000 message packets per second, but some swamped sites with more than 600,000 packets every second. One site received 102 attacks in a single week, says Science Observer.

Sites with addresses ended in .net or .com received most of the attacks, but Moore and his colleagues discovered that 10 to 20 percent of the DoS attacks targeted home computers. Moore thinks that´s related to Internet Relay Chat (IRC), where there could be upset users trying to get revenge or retribution for something said or done. The UCSD team noted an important feature of the phenomenon of DoS, namely: "There is a lack of good automated defensive technology. Detecting, diagnosing and responding to denial-of-service attacks is still largely a manual procedure. That increases both response time and cost while also reducing the number of attacks that can be addressed." He adds: "While the attackers have embraced automation through worms, viruses, tools for breaking into machines and distributed control platforms, this same level of technology has been slow to emerge on the defensive side."

Note: this article does not deal with a similar important problem, the distributed denial-of-service attacks, for reasons of space.

Here in InfoSatellite, you can read on the topic "Security" the article "Basic Security Measures" or check if your system is secure or not in "Online Security Check."

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