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File creation timesFile creation timesPosted Jul 29, 2010 19:31 UTC (Thu) by hppnq (guest, #14462)In reply to: File creation times by butlerm Parent article: File creation times
Not really. It allows you to easily verify whether a file has been tempered with by an attacker.
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File creation times Posted Jul 29, 2010 20:45 UTC (Thu) by sync (guest, #39669) [Link]
No. When the attacker overwrites (not replace) the file the creation time doesn't change.
File creation times Posted Jul 29, 2010 21:10 UTC (Thu) by tialaramex (subscriber, #21167) [Link]
Worse, the attacker is not obliged to obey your conventions.
Just because _you_ don't want to change the create time, doesn't prevent the attacker from doing so. "Oh," you say "but there will be no syscall". Again, this is a problem for you, the legitimate user, but not for the attacker, he can just force the relevant blocks out to disk, scribble on the raw disk, and let them be read back in again - voila!
File creation times Posted Jul 30, 2010 7:14 UTC (Fri) by hppnq (guest, #14462) [Link] It's quite likely that you can't use ctime to verify that a file has NOT been tempered with. If someone is able to scribble something poetic on a raw device, it makes no sense to worry about the ctime on /bin/ls. This should not be trivial for an attacker, of course.But obviously, if a ctime has changed unexpectedly, there's no doubt someone messed with the file, or the kernel.
File creation times Posted Jul 30, 2010 11:50 UTC (Fri) by sync (guest, #39669) [Link]
Now you are talking about change time (ctime) not creation time.
And ctime changes doesn't means that someone messed the file. There are a lot of false positives:
And of course ctime should not be user changeable. But not for security reasons.
File creation times Posted Jul 30, 2010 16:49 UTC (Fri) by hppnq (guest, #14462) [Link] Now you are talking about change time (ctime) not creation time. Ah, I assumed indeed that the original comment was about ctime. I was never talking about creation time. Sorry for the confusion.
Of course not.
Look up some real-world examples of intrusions and how they were detected, or delve deeper into forensic discovery with The Coroner's Toolkit or its successor The Sleuth Kit. Fascinating stuff.
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