The 10 Biggest Security Risks You Don't Know About

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No Safe Haven: Threats Plague All Platforms

Danger level: High | Likelihood: Low | Target: Windows, Mac, and Linux users

Illustration: Steven Lyons

Mac and Linux users have been understandably complacent as Windows users suffer a seemingly endless series of attacks that exploit hole after hole in Microsoft's operating system. But these alternative OSes--once considered safe computing havens--increasingly must cope with their own problems.

The Mac is under attack as evildoers aim at the 70-odd reported security holes in OS X. One of these vulnerabilities was exploited in February by the first piece of malware to hit OS X Tiger: the so-called Oompa-loompa instant-messaging worm. And while Internet Explorer users are probably well accustomed to hearing reports of new browser bugs that could allow "remote code execution" (read: giving an attacker control of your PC), Mac users now need to beware as well--the most recent of Apple's three major security patches this year closed one such hole in the Safari browser.

Linux has a case of worms, too; the number of malicious programs targeting that OS doubled between 2004 and 2005. Rootkits, the looming threat for Windows PCs, actually trace back to attacks meant to take surreptitious control of the administrative "root" user on Unix OSes. Also, while being able to run your own personal Web server is part of the open-source draw, doing so can allow crooks to hijack your site or take control of your PC.

The latest twist is cross-platform malware: single programs that can assault two or more types of systems.

A proof-of-concept virus that attacks both Windows and Linux appeared in April. The virus, created by antivirus firm Kaspersky, contains no payload and does no damage. Known variously as Virus.Linux.Bi.a and also Virus.Win32.Bi.a, it infects just a single type of Linux file format (ELF) and a single type of Windows file format (PE). And it's based on old Linux elements that aren't part of newer systems. Still, it was enough of a wake-up call to prompt Linux creator Linus Torvalds to write a fix.

Windows' ubiquitousness means that malware targeting its many security holes has the greatest chance to infect the most PCs. But as alternative operating systems grow in popularity, they become more attractive targets, too.

OS Holes Abound

The number of security advisories issued for the OSs below show Microsoft is not alone when it comes to vulnerabilities, but Apple seems to patch more promptly.


  1. Consider using a Mac or Linux antivirus program, such as Panda Antivirus for Linux and Mac products from vendors such as McAfee and Symantec. If nothing else, you'll be a good neighbor and help stem the flow of Windows viruses.
  2. Whatever your OS, keep it fully up-to-date and patched.
Andrew Brandt, contributing editor for PC World, writes the Privacy Watch column.
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