Security when Using an External Boot Disk

Question

Hi All.
I'm about to purchase a new external hard drive for using as a boot disk and was wondering what securities you can now enforce on a partition with OSX 10.6
The main purpose for the external boot disk is for creating a shared usage resource for running applications. As I will be allowing others to use this drive, I am concerned about the security implications of using it with one of my macs, mainly because of viruses and data corruption.
I know that partitions/external drives used for booting Windows are secure because the windows partition is set to read only for other partitions/drives, preventing "infections".
The question is: Can I set the permissions/security for an external boot disk (OSX 10.6) partition so that if I use it with one of my machines, my internal hard drive will be secure from any viruses, corruptions, etc.
If you can, or if there's anything else I can do to the same ends, please can you tell me how (or post a link to instructions/advice)
Thanks in advance for your help.

Answer 1

Thomas A Reed wrote:
I'm glad you enjoyed reading my [Mac Virus guide|http://www.reedcorner.net/thomas/guides/macvirus>, but it sounds like it has not adequately impressed on you the extreme rarity of Mac malware at this time, or the low threat level. Also, it sounds like you're still operating under a couple misconceptions. Firstly:
The external boot drive idea seemed like the perfect solution. As it's the boot drive, when it's used, it's permissions will be enforced on the user. Theoretically this should provide solid protection from trojans, obviously not for that actual boot drive, but for my internal HD.
Keep in mind that trojans are not viruses... they are not going to spread themselves by attaching to other files. (Though, if they did, I'm not sure why you think they wouldn't be able to affect drives other than the boot drive.) Also, malware today is not a juvenile prank aimed at erasing your files. (Though, again, if it was, I'm not sure why you think it wouldn't be able to affect drives other than the boot drive.) Malware these days is big business, aimed at stealing your personal information or turning your machine into a slave to help send spam or crack other machines.
You also say:
The main threat will be from freeware
For this reason, AV software can actually cause more risk. No AV software catches all malware, so by becoming over-reliant on it, you don't use the filter between your ears. That filter is all that is needed to avoid Mac malware. And keep in mind that Mac malware is extremely rare.
@Thomas. I know how rare mac malware is, after a decade and a half of using macs I've yet to knowingly come across any.
The reason for my assumption that a secondary boot drive would afford me more protection is: As with any partition you can set the read/write permissions. Without write permissions, surely a virus cannot copy itself onto another drive.
The important thing is that this secondary boot drive would not contain any personal details, and would not be used for online purchases/transactions. Thus if malware was downloaded onto the drive, it couldn't access sensitive data.
Furthermore when I've finished working with someone, I can scrub the drive and restore from a cloned backup, thus eliminating any maleware that might be on it.
The most common freeware that will be downloaded will be codecs for video. There often is no way to get around this. If the person I'm working with has video in an unsupported format they need this code to use their footage. As you pointed out this is the kind of area that people use to hide trojans (not just for ****!).
Not at all. Again, trojans are not viruses... they do not show up on your machine attached to other software.
This has confused me a little. I thought that Trojans are written as a pice of code that can be hidden within another program. eg. A video encoder program can contain malware but still also behave like a normal encoder when you run it?
Thanks again for your help.