Thursday, 18 June 2015

Google Drive falsely reports that some .7z files are infected!

I recently changed from using .zip files to .7z files (using the 'Ultra' compression setting) because .7z LZMA compression made much smaller files (e.g. 30MB .zip reduced to under 20MB if I use .7z + 'Ultra' compression) and thus made it quicker to download for everyone.

However, Frettt (who translated the German Strings.txt file in E2B) pointed out to me today, that if he attempted to download the Easy2Boot_V1.70DMPS.7z file from Google Drive, it reported it as 'Infected'!

Previously I used .zip files and these did not cause a problem - in any case Google Drive only checks files less than 28MB in size and the E2B DPMS .zip file was 30MB.

I experimented by dividing the files in half and using .7zip to zip up the two halves from the Easy2Boot source files in an attempt to find out what files Google did not like. I then downloaded the two files from Google Drive, but it did not report either file as infected!

I then tried various, different compression settings in 7Zip on the original E2B DPMS source files.

I created the .7z file, uploaded it to Google Drive and then downloaded it again. If it gave an 'Infected' warning, I then added 'FAIL' into the filename, if it did not give the 'Infected' warning, I added 'PASS' to the filename.

Here are the results - each file has identical contents:

It seems highly compressed settings cause problems. So I settled on these settings in 7Zip:

So instead of 17MB, we get a 20MB file - but at least it is not reported as infected!

Of course, it is possible that with a different set of files, Google Drive may report the .7z file as infected, even with these settings...