On this page, you can potentially reduce scanning time by specifying certain types of files that should not be scanned.
Do not scan verified system DLLs – if this box is checked, system library files will not be scanned.
Use transient caching – if transient caching is used, a file that has been scanned, and in which no infection was detected, will not be scanned again the next time it is accessed. However, this is only valid until the next virus definitions update, as the file may contain an infection that was not previously detected but which may be detected based on the new virus definitions. Also, information that the file is clean will only be stored in the computer’s operating (temporary) memory. This means that when the system is restarted the information will be lost, therefore the file will also be scanned again the next time it is accessed after a system restart. This box is checked by default; if you want files to be scanned every time they are accessed, this box should be unchecked.
Use persistent caching – if persistent caching is used and a file is verified as clean, this information will be stored in the permanent memory. This means it will not be lost after a system restart and it is also not affected by virus definition updates. Verified clean files are files which are guaranteed not to contain any virus infection e.g. some operating system files, files signed by trusted publishers, or other files covered by the avast! whitelist. This box is checked by default; if you want all files to be scanned regardless of their trust status, this box should be unchecked.