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4 replies to this topic

#1 BlaKK


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Posted 17 January 2011 - 02:25 PM

This is something that has always mystified me. I am curious to know whether or not a piece of malware can escape one it has been quarantined?

Thanks in advance.

Edit: Moved topic from General Chat to the more appropriate forum. ~ Animal

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#2 Sightless


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Posted 17 January 2011 - 05:43 PM

I don't believe so.
I've never heard of it happening, although I suppose there may be an exception out there somewhere.
You should delete quarantined malware after you are sure it is not a false positive (sometimes files can be quarantined that are an essential part of a program(.

#3 PropagandaPanda


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Posted 17 January 2011 - 07:12 PM


Sightless is right. Simply put, it can't.

In some cases, it may appear that it has happened because you were reinfected somehow, perhaps from the malware being incompletely removed.

With Regards,
The Panda

#4 Didier Stevens

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Posted 18 January 2011 - 04:18 AM

With escaping from the quarantine, I assume you mean that a quarantined malware sample gets executed and (re)infects your machine?

AV companies protect their quarantine folders with ACLs, by renaming files and other proprietary techniques, so that you can't get access to that folder and malware samples stored within can't execute.

I can come up with 2 theoretical, exceptional situations where a sample might escape, but this is nothing to worry about. If you're interested, I can provide you more details.

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#5 quietman7


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Posted 18 January 2011 - 02:18 PM

When an anti-virus or security program quarantines a file and moves it into a virus vault (chest) or a dedicated Quarantine folder, that file is safely held there and no longer a threat. The file is essentially disabled and prevented from causing any harm to your system through proprietary security routines which may copy, rename, encrypt and password protect the file as part of the moving process as Didier Stevens explained.

Quarantine is just an added safety measure which allows you to view and investigate the files while keeping them from harming your computer. One reason for doing this is to prevent deletion of a legitimate file file that may have been flagged as a "false positive" especially if the scanner uses heuristic analysis technology. Heuristics is the ability of a scanning program to detect possible new variants of malware before the vendor can get samples and update the program's definitions for detection. Heuristics uses non-specific detection methods to find new or unknown malware which allows the anti-virus to detect and stop if before doing any harm to your system. The disadvantage to using heuristics is that it is not as reliable as signature-based detection (blacklisting) and can potentially increase the chances that a non-malicious program is flagged as suspicious or infected. If that is the case, then you can restore the file and add it to the exclusion or ignore list. When the quarantined file is known to be malicious, you can delete it at any time by launching the program which removed it, going to the Quarantine tab, and choosing the option to delete.

Keep in mind, however, that if these files are left in quarantine, other scanning programs and security tools may flag them as a threat while in the quarantined area so don't be alarmed if you see such an alert. Just delete the quarantined items after confirming they are malware and subsequent scans should no longer detect them.

Edited by quietman7, 18 January 2011 - 02:20 PM.

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