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If you create a bootable live CD/DVD for an OS such as Linux or Windows, is that more secure than a live USB that does the same thing? What if the disk is a CD-R or DVD-R as opposed to a CD-RW or DVD-RW? What I am interested in is malware in-place modifying the media on which the live OS is stored, and possibly infecting machines on which the live disk or USB is inserted into and booted from.

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Note that you can buy pen drives with a physical R/W switch. Using those would be equally secure to plain CDs or plain DVDs. (vs CD/DVD-RW). – Hennes Oct 23 '12 at 0:37
Unfortunately, this appears to be a pretty rare feature; Kanguru and maybe one or two others have something like this. It's strange with all the USB viruses and worms spreading that this isn't more common. – anon Oct 23 '12 at 1:12
Aye. Finding a pen drive which is both fast and has this feature is a challenge. One which has evaded me. :( And the difference between some slow USB drives (read 3MB/sec) and fast ones (read: 90MB/sec) is huge. – Hennes Oct 23 '12 at 1:25

Yes and no. You cannot alter the contents of a livecd - so if you get attacked by malware, it'll only affect you that session. Remove the cd, and the malware is 'lost' when you reboot, only having existed in the ram. Any malware that alters a disk needs to be aware of the disk, and somehow write to the disk thats being read. Its just too complex, since the malware writer wouldn't know what environment he's attacking.

Many liveusb implementations tend to involve some sort of 'write filter' or having seperate OS areas for a 'base system' and additional files to save on writes. The base system is probably safe unless the malware is specifically designed to affect it. The OS areas arn't. I'd say a 'standard' windows winpe/barpe disk should be 'reasonably' safe, as would a linux one.

In either case I've not heard of malware being specifically designed to affect a livedisk so far. Its just too muck work, for too little benefit.

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If it's a CD-WR, what's to stop the malware from altering the contents of the CD to propagate itself? – anon Oct 23 '12 at 0:50
Firstly, it'll need to be aware that its a cd-r. Secondly the cd-r would need to be burnt to a format that allows appending to the image - in this case packet writing. Third, it would need to know what OS it is, and hook into its burning software to do this. – Journeyman Geek Oct 23 '12 at 0:52
Use a CD-R, write it as DAO, no multi-session and verify the DAO write has closed the disk for no further writes. Using a CD-RW for your boot disk is a waste of resources anyway. – Fiasco Labs Oct 23 '12 at 1:05

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