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Worm Threat Forces Apple to Disable Software?

When an online identity (group of identities) known as InfoSec Sellout made grand claims of a proof of concept worm, dubbed Rape.osx, that targets OS X, it led to a lot of heated argument and drama - including anonymous death threats and an accidental deletion of their blog. While there has still been no external proof of their claims, or appearance of the worm outside of their testing environment, the information that accompanied the original claims pointed to a vulnerability in mDNSResponder as being the underlying vulnerability exploited by Rape.osx.

Even though Apple had addressed various vulnerabilities within mDNSResponder in different Security Updates, the claims being made were that Apple had failed to adequately address a set of vulnerabilities - only patching specific attack vectors rather than the underlying problem.

Although InfoSec Sellout has effectively disappeared from the Internet (their blog has been suspended by Google), it appears that the drama and initial disclosure may have forced Apple to disable an OS X system component with their most recent Security Update (Security Update 2007-007). Contained within Apple's knowledgebase article accompanying the release, is information about changes to mDNSResponder behaviour following the application of the Update.

Seeming to closely follow the information disclosed by InfoSec Sellout, Apple's mDNSResponder update addresses a vulnerability that can be exploited by an attacker on the local network to gain a denial of service or arbitrary code execution condition. Apple go on to identify that the vulnerability that they are addressing exists within the support for UPnP IGD (Universal Plug 'n Play Internet Gateway Device - used in port mapping on NAT gateways) and that an attacker can exploit the vulnerability through simply sending a crafted network packet across the network. With the crafted network packet triggering a buffer overflow, it passes control of the vulnerable system to the attacker.

Rather than patching the vulnerability and retaining the capability, Apple have completely disabled support for UPnP IGD (though there is no information about whether it is only a temporary disablement until vulnerabilities can be addressed).

There has already been some chatter on various mailing lists about this seemingly-odd move by Apple, with the responses primarily indicating that observers have found this particular method of addressing a vulnerability to be humorous.

It is interesting to note that Apple have not attributed any external party for the identification and reporting of the vulnerability, and the relevant CVE entry (CVE-ID: CVE-2007-3744) shows only that it is a reserved entry - with no information about who might have registered the CVE ID and no information about what the entry relates to. If the information reported by MITRE is accurate, then it points to the CVE entry being created prior to the public disclosure of the existence of Rape.osx (12 July versus 16 July). This may be coincidental, but it might provide some insight about the spread of information about the vulnerability if the party responsible for creating the ID is disclosed.

2 August 2007

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