Is the PowerPC-based iMac G5 less susceptible to attack from criminals than the Intel-based iMac models?

Although security is subject to numerous variables, in general, the vast majority of exploits are designed to target a particular operating system.

Because both the PowerPC-based iMac G5 and Intel-based iMac models are designed to run versions of MacOS X, the vast majority of security strengths and weaknesses should be roughly equivalent. This assumes that both systems are configured by end users in the same way.

However, it is possible that the Extensible Firmware Interface (EFI) used by the Intel-based iMac systems could be attacked. There is no particular reason to believe that EFI is less secure than Open Firmware used by the PowerPC-based iMac G5, but because EFI is used on Intel-based Macs and a variety of Windows PCs, EFI is a much larger target. Simply because EFI is a larger target, there is a greater chance that someone would be willing to devote the time needed to develop an EFI exploit that might damage both Windows PCs and Intel-based Macs.

Nevertheless, a C|Net article quotes a variety of security experts who conclude that such attacks on "lower-level system software. . . are rare".

If Windows is installed and running on the Intel-based iMac, the system can be compromised using the same methods that can affect any other Windows PC. The PowerPC-based iMac G5, on the other hand, cannot boot Windows, and as a result, cannot be made subject to the various security holes that tend to plague the Windows operating system.

An InfoWorld report quotes a security expert who first acknowledges that the risk of "crossover" viruses is overinflated, but then he remarks:

Mac and Windows each have their own vulnerabilities, and though I think we'll see a [Mac OS-to-Windows] crossover proof-of-concept before the end of this year, there's just not a lot of value in it for an attacker.

Effectively, given the small number of systems that are capable of running both MacOS X and Windows, this expert thinks that few are likely to bother writing attacks that operate in such a manner. He also mentions the possibility of an attack that could damage the partition table, potentially causing problems for any operating systems installed on the system.

Ultimately, the fact that the PowerPC-based iMac G5 systems use a more "obscure" architecture and cannot boot Windows may make them slightly "less susceptible to attack" than the Intel-based iMac models. Realistically, however, when running MacOS X and configured properly the overall security of both models essentially is comparable.