Could a Worm on Mac or Linux Ever Get Traction?

By Larry Seltzer  |  Posted 2004-05-06 Print this article Print

We saw a series of Macintosh security vulnerabilities exposed this week. Some of them are quite nasty, but the nature of the bug notwithstanding, it's unlikely to be as widely exploited as a Windows problem.

Will we ever see something like the Sasser worm for the Macintosh or Linux? Its an interesting question, and not just for academic reasons. Undoubtedly, many people who choose these platforms do so because they think it immunizes them from the sorts of attacks Windows users must deal with. This past week saw the announcement of several vulnerabilities in Mac OS X, some extremely serious. The first, a heap overflow in QuickTime reported by eEye, could allow an attacker to run arbitrary code in the context of the user running the QuickTime player. The eEye advisory takes Apple Computer Inc. to task for understating the importance of the bug—for which Apple has supplied a patch—and for the obviousness of the vulnerability. Indeed, based on developer documentation cited by eEye, it sure quacks like a heap overflow.

A far scarier vulnerability was reported by @stake Inc. Its a remotely exploitable stack-based buffer overflow that could allow a user to execute arbitrary code as the root user.
This could be the big one. Based on this, you really could build a Sasser-type worm, one that travels from computer to computer without the user having to do anything stupid such as launch an attachment. The whole thing could happen at night while youre asleep.

Click here to read more about the Sasser worm. The overflow is in the Apple Filing Protocol (AFP), which provides file-sharing services for both clients and servers similar to SMB/CIFS on Windows and Samba. Its true that AFP is not enabled by default, but its enabled on anything sharing files. Certain requests to authenticate with the target system can overflow it simply by specifying a pathname longer than the specified length. This one, again, shouldnt have made it past any serious scrutiny. It works on multiple OS X versions, and it can give the attacker root privileges. Apple has patched this, too. See the Apple Security Updates page for more details and for the patches.

Interestingly, Apple released several other patches this week. None of them appears to be as serious as the two above, but its hard to be comfortable with that since Apple appears to understate the importance of the AFP problem. For example, the companys advisory says that the point of the patch is "to improve the handling of long passwords." Because of this, security firm Secunia has chosen to assume that all of the vulnerabilities are more serious than Apple concedes.

Next Page: A Mac worm would not spread as quickly.

Larry Seltzer has been writing software for and English about computers ever since—,much to his own amazement—,he graduated from the University of Pennsylvania in 1983.

He was one of the authors of NPL and NPL-R, fourth-generation languages for microcomputers by the now-defunct DeskTop Software Corporation. (Larry is sad to find absolutely no hits on any of these +products on Google.) His work at Desktop Software included programming the UCSD p-System, a virtual machine-based operating system with portable binaries that pre-dated Java by more than 10 years.

For several years, he wrote corporate software for Mathematica Policy Research (they're still in business!) and Chase Econometrics (not so lucky) before being forcibly thrown into the consulting market. He bummed around the Philadelphia consulting and contract-programming scenes for a year or two before taking a job at NSTL (National Software Testing Labs) developing product tests and managing contract testing for the computer industry, governments and publication.

In 1991 Larry moved to Massachusetts to become Technical Director of PC Week Labs (now eWeek Labs). He moved within Ziff Davis to New York in 1994 to run testing at Windows Sources. In 1995, he became Technical Director for Internet product testing at PC Magazine and stayed there till 1998.

Since then, he has been writing for numerous other publications, including Fortune Small Business, Windows 2000 Magazine (now Windows and .NET Magazine), ZDNet and Sam Whitmore's Media Survey.

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