"Secure delete" function in
context menu and in "File tools" submenu is intended for deleting file
and folders in a secure way, overwriting multiple times disk sectors
where information is stored, function also known as file shredding, or
This is a
permanent and unrecoverable deletion of data, not allowing any
of erased information from disk - similar to software like
Non-secure deletion, as usually implemented on most operating systems,
is a plain de-referencing of the file name in the file system
allocation structure, leaving unaffected the data stored on disk until
it is, by chance, overwritten by new data.
This allows information to be recovered by data-recovery softare if not
overwritten with fresh data, otherwise specialized hardware recovery
tools can be used to scan the surface of the disk (or memory cells) to
detect with a reasonable range of certaininty up to a few previously
stored states in the same memory unit.
PeaZip's secure data delete utility accepts multiple files and/or
input and provides
multiple overwriting of file data with random data stream (AES256 CTR)
forcing flush to disk each time, then replacement of content with
randomly sized random data to fake file size, and multiple renaming of
the file with random string.
PeaZip file explorer query the filesystem with its own custom
functions, based from low level primitives rather than relying on
operating system's high level file browsing API; that (in some
instances) enables the program to show data otherwise not visible - not
simply hidden, but otherwise purposely protected or made not accessible
to system file manager, by the operating system itself or even
At current level of development however, PeaZip cannot unlock files
locked by other processes (requires to find and kill the process
locking the file) in order to remove undeletable files - this has be
done separately by dedicated, system-specific utilities.
deletion very carefully, since permanently deleted data will reasonably
recoverable with known - hardware or software - data recovery tools.
Please note that secure file deletion doesn’t overcome all known
risks of data leakage, since may exist copies of the data as temporary
files saved by application that accessed the file, or as not securely
deleted older version of the file, or cached by the system: clearing a
file cannot affect that orphaned data,
which can be recovered with software
utilities or specific hardware probes.
Flash units (as solid state disks SSD or USB keys) usually re-allocates
sectors for writing
transparently for the software, in order to reduce unit’s wear since
flash units have a shorter lifespan in terms of writes; this doesn’t
allow to efficiently physically overwrite original content, reducing
the efficiency of file shredding.
In this case only erasing the whole disk (with one or more random
data passage on all the free space) would be effective, but this
can be very time consuming and, for flash based or hybrid drives, it
will lead to
fast wear and reduced lifespan of devices.
Cloud and remote
Data stored on remote servers (as in cloud services) may be subject to
periodic backup unknowingly to users, so please
consider that copy of the data before erasure may exists on servers,
out of the reach of users, if such services are used, unless
differently specified in terms of service.
Moreover, as terms of services are often subject to variations, and
limitations in user's rights depending on the laws applying to the
provider of the services (such as, possibly, do any effort in providing
access to user's data under some circumstances), it is highly
recommended encrypting data on user's
end before upload to any external machine, even when encryption is
offered as service by the remote storage / cloud service provider.
"Quick delete" is provided as
an alternative to secure deletion by PeaZip, this action deletes files
and folders without moving data to the
recycle bin, which is faster and increases security against forgetting
of recycled data.
Like secure deletion, fast deletion does not allows to recover data
from the system's recycle bin, but as it is not intended for securely
sanitizing data, it is feasible to recover data destroyed with fast
delete using appropriate undelete utilities.
Secure delete is
also available for free
space: the free disk space on the specified unit is physically
overwritten multiple time with a random stream as in secure file
deletion - it may take several minutes on large disks - likewise
software as OS X
Disk Utility to erase free
space, or cipher
/w command in
In this way leftover remanants of data previously saved to disk
reallocated sectors, ...) are replaced by random data, making analysys
of free space useless.
This level of security is not matched by formatting the volume, as
quick format routines does not overwrite existing data, which can be
recovered with specific utilities, and even more through format
utilities does not implement a multi-pass overwriting of free space
with random data, making previous state of the disk recoverable with
suitable hardware scanning equipment.
delete files and free space is also available, the function
overwrites data with all zeroes before deletion. It is
recommended to be performed before saving disk images either of
physical machines (for backup and disaster recovery) and for virtual
disk images, as more uniform (zeroed) data is much more easily
compressible - learn more optimizing virtual
machines and disk images backup
External online resources: data erasure, and data
entries, disk sanitization software examples: OS X
Disk Utility, and
Topics and search suggestions: secure delete sensitive data,
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space, secure volume deletion, DoD-compliant file
shredding, disk wipe,
application, prevent data recovery, avoid undelete, secure disk unit
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