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Education In America Authors: yomi omika, Darrah Deal, Student Lance, David Miller, David Miller

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SCO's "DDoS Attack" - Was It or Wasn't It?

Why didn't SCO's Linux block all "SYN flood" attacks, ask experts.

Both The Age and The Sydney Morning Herald, two of the biggest news sites in Australia, have already begun asking questions about yesterday's outage at the SCO Web site, which SCO Group described in a statement as "a large scale distributed denial of service (DDoS) attack."

In a piece bylined Sam Varghese and dated today December 11, The Age reports:

SCO said it was working with its ISP to restore service and that the site was unavailable due to a SYN flood attack.

IT professionals have, however, cast doubt on SCO's claims as the operating system on which its website is hosted, Linux, has the ability to block all SYN attacks.

Additionally, it has been pointed out that Cisco, the router manufacturer, has patches in place for its hardware to prevent such attacks. If SCO is facing such an attack then it appears that elementary precautions have not been taken, the pros say.

Web stats provider Netcraft has a graph of the activity before and during the period when SCO says its site was being DDoSed.  

The incident affected SCO's Web site, e-mail, intranet and customer support operations and SCO said that the particular DDoS used is known as a syn attack and used "several thousand servers [that] were compromised by an unknown person to overload SCO's Web site with illegitimate Web site requests."

Steve McInerney, an Australian security expert consulted by Groklaw, however, raises questions.

McInerney, who worked for six years as the Technical Security member of the IT Security team for Australia's Department of Defense and more recently was one of the senior designers/firewall/security experts at a company that manages Australia's largest federal government-certified Internet gateway, is of the opinion that "SCO are NOT suffering a DDoS attack. Specifically not one that they have described. It looks to me like someone has accidentally kicked a cable out of it's socket or similar. Or a HDD failure or...."

"Speaking as a Sysadmin/Firewall guy," McInerney says, "my first priority in any attack is to solve the problem - not issue a press release."

Such debating points aside, here is McInerney's technical rationale, verbatim:

A 'SYN Flood' attack is an attack that attempts to stop a server from accepting new connections. It's quite an old attack now, and has been relegated to the 'That was interesting' basket of attacks. A very simple analogy of a SYN attack: You have two hands, you are thus able to shake hands with at most two people at any one time. A third person who wants to shake your hand has to wait. Either you or one of the first two people can stop shaking hands so as to be able to accept the third person's handshake.

In this instance SCO are claiming that 'thousands' are doing something similar to their web server. This is, in and of itself, plausible. Unfortunately if we look closer there are a few problems with this claim of SCO's.

As stated above, the attack is quite an old one. Patches to all Operating Systems that I'm aware of, do exist to stop this sort of attack. For instance, a CISCO document describes the attack and provides ways to stop it. Note the lines: 'Employ vendor software patches to detect and circumvent the problem (if available).' This means, quite simply, that patches exist to mitigate this attack. Why hasn't SCO applied them?

Further SCO States: "'The flood of traffic by these illegitimate requests caused the company's ISP's Internet bandwidth to be consumed so the Web site was inaccessible to any other legitimate Web user.'

Interesting. If their bandwidth is consumed, then any servers nearby will also be inaccessible. That is www.sco.com has the IP address of 216.250.128.12 and ftp.sco.com has the IP address of 216.250.128.13 so the two servers are side by side, probably even on the same physical network hub/switch. Note that there is no room for a broadcast, etc., address - these servers are on the same subnet - i.e., on the same network device (hub/switch).

Unfortunately for SCO, from Australia, ftp.sco.com is highly responsive. No bandwidth problems there that I can see - even though www.sco.com is still unavailable. The evidence then, is that their bandwidth is fine.

So what about just the SYN flood? Well, even with patches, to successfully conduct a SYN flood you would tend to chew up available bandwidth anyway, which we aren't seeing. So I have quite strong doubts about the accuracy of this information. I feel quite comfortable in stating that SCO are NOT suffering a DDoS attack. Specifically not one that they have described. It looks to me like someone has accidentally kicked a cable out of it's socket or similar. Or a HDD failure or....

Dealing with an DDoS atack when your bandwidth is NOT eaten up is fairly simple. A quick and dirty script to read your firewall log(s) for incoming addresses that are trying the SYN attacks is fairly easy. Adding those IP addresses to a quick block list is also easy.

After this, and other, opinions, the counter-allegation that SCO was perhaps "faking DOS attacks to make Linux community look bad" is now doing the rounds of the Internet. LinuxWorld will endeavor to keep you abreast of whatever consensus on the facts is eventually reached.

More Stories By Linux News Desk

SYS-CON's Linux News Desk gathers stories, analysis, and information from around the Linux world and synthesizes them into an easy to digest format for IT/IS managers and other business decision-makers.

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