mchain
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As does adobe flash full installer, most program installer programs use a password, so if avast! does not know the password, it cannot look inside the installer file and so reports the ‘cannot scan error’. This password is internal and only known to the installer program so as to be able to open and extract the compressed files to run the install program.
IF avast! knows the password==>THEN the archived file/installer program is opened and scanned by avast!
IF avast! does not know the password==>THEN the archived file/installer program is not opened and scanned by avast!
Avast! then reports the scanning error, as it is supposed to be able to scan all files on the hard drive, but fails to do so here.
It cannot when the password is unknown. Passwords are used in archived files/installer programs to protect them from malicious modification by people with malicious intent and also maintain file integrity by preventing these people from easily opening the file to make any undesirable changes to it.
The only time an archived file/installer file can be malicious is when it is opened by the user of the system. Avast! File Shield will automatically block any known malware being unloaded and uncompressed at the moment it is run from an archived file.
So, if avast! cannot scan an archived file because it does not know the password, don’t worry. Archived files cannot harm your system just sitting there; they must be opened by you to cause harm, and avast! is ready to block any malicious or suspicious files from running at the moment they are opened on your system, if detected, to prevent damage to your system.
Archived files=inactive files=cannot harm your system in an inactive state even if malicious.