Malicious Mac OS X Script Poses Threat

A malicious script for Apple Computer Inc.s Mac OS X has been discovered that is capable of harvesting passwords and installing remote control software and security backdoors onto a users machine.

Renepo, which Symantec Corp. has classified as MacOS.Renepo.B and Mac user groups are calling Opener, is a Unix shell script that attempts to turn off OS Xs firewall and various accounting options, then downloads and installs various remote control and password cracking applications. It then attempts to create an admin-level user for later use and harvest as many passwords and user details as possible.

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Anti-virus companies warned that, although not yet found in the wild, Renepo represents a potential threat. "Renepo makes so many security-related changes to your systems that all bets are off once you have been compromised. Because the worm attempts to harvest user, configuration and password data for a wide range of applications, it represents a huge security headache for all administrators, creating a backdoor to leave infected computers vulnerable to further attack," said Graham Cluley, senior technology consultant for anti-virus specialist Sophos. Both Sophos and Symantec have updated their products to detect and eliminate Renepo.

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However, despite being undoubtedly malicious in intent, Renepo has no effective method of automatically propagating itself and so poses little threat at present. Although it attempts to copy itself to any mounted drive (including those on servers), it relies on someone with administrator privileges running it in order to install itself to the /Library/StartupItems folder, which will ensure it runs every time the Mac is used. "We believe the circumstances under which it will be able to spread are quite small. We dont believe it is spreading in the wild, and we think it is unlikely to," said Cluley.

Although the Mac has yet to see anything other than a fraction of the security issues that have bedeviled Windows, this year has seen several alerts that have heightened concern over the potential for new viruses and malware on the platform. In May, the first known malicious Trojan for OS X—an AppleScript posing as a copy of Microsoft Office 2004—was discovered. And Apple has released several patches to cure known security holes, including one in May that could potentially allow hackers to execute any code on a users machine remotely.

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Sophos Cluley cautioned against Mac users becoming complacent: "Clearly the various people behind Repeno have been working on their malicious script for some time, and its quite possible they will refine it and use it maliciously in the future."

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