SLAMorris Final Thesis After Corrections.pdf - Cranfield University

5.6.2 The modification of subrecords
This subsection looks at the modification of information stored within the cache.
In order to study the causes of modification to the thumbnail cache, clones of
the virtual machines from Section 5.6.1will be used. Therefore the experiments
start with data within the thumbnail cache; in order to assess how this data is
modified the original source files will be modified during a variety of experiments
described in this sub-section.
Modifying the contents of a file
A randomly selected group of files on the virtual machine were altered using
appropriate pre-installed software. A list of the 500 user-generated files added
to the virtual machine was stored in a text file. A small program was written to
randomly select 10% of the files; the names of the selected files were stored in
a second text file. Each of the selected files was opened using the default
editing application for that file type; image files were modified by making the
images entirely black, for text based file types the information within the file was
copied and pasted underneath the original data. After the files were modified
they were saved and the editor closed. Once all modifications had been
completed the directories containing the user generated images were then
viewed using the file manager. The modification caused the last modified time
of the file to be updated. Both on Ubuntu and Kubuntu, this caused the affected
subrecords to be altered, to show the current state of the file; all the files
showed the modified black images or repeated text in the file browser.
Modifying the files URI
In order to ascertain the effect of modifying the file’s URI, the virtual machine
was populated with 500 user generated files which were copied off a USB stick
and into the user’s documents directory. A directory named ‘test’ was created
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