What is a decompression bomb.

[Lisandro]

By examining 1) the reason given by avast! for not being able to scan the files, 2) the location of the files, you can get an idea of what program they relate to. You may need to expand the column headings to see all the text.

Files that can't be scanned are just that, not an indication they are suspicious/infected, just unable to be scanned.

Also, the packaging of the file could have some error, or use a non-standard pattern...
avast can't scan files that are password protected, it doesn't know the password.

[sysusr]

I'm new around here so I apologise if these forums are just inactive and I need to give it more time, but could anyone shed some light on my previous question?

[DavidR]

We as avast users like yourself don't know the parameters that avast would use to determine what would be considered a decompression bomb/Highly compressed file. That is why I believe no one has answered specifically.

The main thing is that there is nothing to worry about.

[hewee]

I just got the "decompression bomb" also.

It is a Big compress EntireBible.tar.gz that is 813MB and has 67 other zips inside of it of the other books of the Bible.
You can see it here.
http://bibleforums.org/MP3/kjv/

It is safe but Avast is not able to get into it to scan but can can the zips inside of it if I take then out of the .tar.gz.

[YoKenny]

Welcome hewee

Unfortunatly "decompression bomb" is bad terminology and just means that it is a large file that needs to be decompressed first and when each component is accessed it will be scanned by avast! for infection.

[DavidR]

I just got the "decompression bomb" also.

It is a Big compress EntireBible.tar.gz that is 813MB and has 67 other zips inside of it of the other books of the Bible.
<snip>
It is safe but Avast is not able to get into it to scan but can can the zips inside of it if I take then out of the .tar.gz.

avast isn't saying it isn't safe, just that it can't be scanned and has been said so many times in this and other topics, that doesn't mean it is suspicious or infected just can't be scanned.

The .gz file size of 813MB in itself isn't large, but with 87 other zips inside to be able to scan those, avast has to unpack them (decompress) and that would be much greater in size than the original file size and that is all that avast is indicating.

[hewee]

Hey good seeing yea YoKenny.

I know the file is safe.
Now I have lots of other zip file with more zips inside of them but not as many and as big as that one so they got scanned OK.

Only other files are ones that are password protected like files from Real Alternative and another 44 MB zip that has a folder with 600 images in it. It says they are password protected and that is true.

[DavidR]

If that is true, then you have nothing to worry about either, avast doesn't know the passwords so can't open them to scan.

[hewee]

If that is true, then you have nothing to worry about either, avast doesn't know the passwords so can't open them to scan.

I already knew that there was nothing to worry about and was just posting about the safe bomb I had. 

[wisconsinbigdog]

Sorry to bring up a dead post, but all these guys only have 2 or 3 compression bombs...is it unusual to have 25 at once?

[DavidR]

Numbers don't matter either, either the file is very large or it isn't and if it would be much larger when decompressed would register the warning.

What does matter is what the file is and is there a legitimate reason for why there are so many.

So if you have a large collection of .ico files a file is an image of a CD, etc. this can be burnt directly to create a copy of the original. Or other very large files.

[Sakurako]

this topic has been posted as file report

 Probably it would be fine when using the file does not require that avast! to be temporary disabled. However, if the file would be used as operating system, service pack, or bootable disk, probably would be better to ensure security by using another antivirus software ~

- Page Link: http://www.microsoft.com/downloads/details.aspx?familyid=F559842A-9C9B-4579-B64A-09146A0BA746&displaylang=en
- File SHA1: B8A3FA8F819269E37D8ACDE799E7A9AEA3DD4529 (checked by PeaZip)
- avast! version 4.8 Home Edition (4.8.1368), 100104-0

P.S. as suggestion, couldn't avast! add "scan selected file" in context menu of the report? ~

[winner2]

My Avast Home edition also detected a file I downloaded as a "decompression bomb". That file was the ubunu desktop 9.10 ISO image i downloaded from ubuntu.com...

[iKarma]

I also have a question about a decompression bomb from my computer.  I was transferring some files from one computer to this one when a decompression bomb popped up and it said it was from a MMORPG that I had been playing for a while and hadn't had any problems with.  When I restarted my computer, I couldn't log into my personal profile that I had the game installed on so I don't know if it's okay to reinstall the game, or if it will just cause more problems.

[DavidR]

My Avast Home edition also detected a file I downloaded as a "decompression bomb". That file was the ubunu desktop 9.10 ISO image i downloaded from ubuntu.com...

It doesn't matter what the file is, just that it is very large and even more so if it were unpacked (high compression ratio) to scan the contents.