When downloading files from the Internet in browsers such as Chrome it seems that they set a flag of some sort on the file telling Windows that the file was downloaded form the Internet and that it might not be safe.
For a lot of files this does not cause a problem, opening the file happens fairly quickly prompting me to enter admin mode for the install if needed.
It seems however that for programs with less “reputation,” maybe they don’t have a digital cert or maybe they have only just been released, Windows takes a long time to open the file. Sitting there apparently not doing anything for up to 10 minutes before it finally decides to open the file.
Of course in this time I might have tried to open the file more than once, in that case both files execute at the same time once Windows decides it has checked whatever it needs to check.
I notice that for these files even opening the properties of the file in Windows explorer is very slow, taking the same amount of time. When the file properties do finally open I see an 'Unblock' option in there. I believe this is the flag causing the problem.
Does anybody know what is causing this and how to stop it? It is very annoying. I don’t really know what is responsible for it, maybe Windows Defender?
This happens on all my Windows machines including a fresh install of Windows 8.1 that was installed yesterday. The only antivirus running on the machine is Windows Defender that came with Windows 8.1. There are no other security, adware or malware programs installed.
An interesting note is that if I use a download manager to download the file it seems that this flag is not set on the file and the files always open straight away.
UPDATE1 (include comments summary):
Chrome: Very slow to open properties / execute file after download
Internet Explorer. After download runs 'security scan' which takes maybe 10 seconds then opens instantly both in IE and Explorer
- Windows Defender
- MalwareBytes (on one machine but not another that is also affected)
- Download Managers (such as Download Ninja), files open straight away, no delay
Possible Causes / Solutions:
Disable Windows Defender:
- This does not seem to have any effect on the time required to open a file
Caused by large file size?:
- The files I am testing this with are only about 5-6mb so I am not sure this is the case
Happens with all files?:
- If it download a well known file such as putty it opens straight away
Enable 'Do not preserve zone information in file attachments' in Policy Editor:
- This stops the 'Unblock' button from being shown in properties but it does not appear to speed up the opening of the file. In my tests after setting this option files still take ~30s-4m to open after download