SLAMorris Final Thesis After Corrections.pdf - Cranfield University

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Start of standard thumbnail cache subrecord Start of subrecord header 000000B0 43 4D 4D 4D30 09 00 0047 F2 B6 FD 97 7E B8 24 CMMM0 Gòý—~¸$ 43 4D 4D4D – subrecord signature 30 09 00 00 – 2352 – complete size of subrecord in bytes 47 F2 B6 FD 97 7E B8 24 -Thumbcache ID 000000C0 20 00 00 0000 00 00 00E0 08 00 0000 00 00 00 à 20 00 00 00 – Size of Identifier string 00 00 00 00 - Size of padding E0 08 00 00 – size of subrecord data in bytes 00 00 00 00 – Unknown but always 00 00 00 00 000000D0 CF 22 EE 39 0B C5 17 37E6 14 5C 59 6B DA F0 B6 Ï"î9 Å 7æ \YkÚð CF 22 EE 39 0B C5 17 37 – Data checksum E6 14 5C 59 6B DA F0 B6 – Header checksum 000000E0 32 00 34 00 62 00 38 00 37 00 65 00 39 00 37 00 2 4 b 8 7 e 9 7 000000F0 66 00 64 00 62 00 36 00 66 00 32 00 34 00 37 00 f d b 6 f 2 4 7 End of subrecord header Page 118
00000100 FF D8FF E000 104A 46 49 46 00 01 010100 00ÿØÿà JFIF FF D8 – JPEG file signature FF E0 - Application use marker 00 10 – Length of APPO field 4A 46 49 46 00 – Identifier – “JFIF” 01 01 – Version number 01 - Unit – dots per inch 00 00 – Horizontal resolution – 0 00000110 00 0000 00 FF DB 00 43 00 05 03 04 04 04 03 05 ÿÛ C 00 00 – Vertical resolution – 0 00 - Horizontal pixel count - 0 00 - Vertical pixel count - 0 …(JPEG image data continues) 000009D0 EB ED 43 E6 E8 75 D1 8E 05 41 7B 46 EE 7F FF D9ëíCæèuÑŽ A{FîÿÙ FF D9 – JPEG file footer End of subrecord The subrecord above shows a standard visual thumbnail subrecord from the thumbcache_256.db file; the image data contained within the subrecord is in standard JPEG format. Whilst the thumbnail cache predominately stores visual thumbnails, the thumbcache_256.db also holds non-standard subrecords. Below is an extracted subrecord which does not contain an image, instead it stores data in a Unicode format, in this particular case it is a GUID. Page 119
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CRANFIELD UNIVERSITY SARAH LOUISE A
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ABSTRACT This thesis establishes th
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ACKNOWLEDGEMENTS “And above all,
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TABLE OF CONTENTS ABSTRACT ........
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6 The structure and behaviour of th
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8.6.1 Stage 1: Preliminary Checks .
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LIST OF FIGURES Figure 1-1:A breakd
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LIST OF TABLES Table 5-1: A summary
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1 Introduction 1.1 Introduction In
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potential difficulty is the identif
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This is followed by a structural an
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Chapter 6 describes the structure a
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Chapter 11 evaluates the methodolog
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2 Related Research 2.1 Introduction
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Generally individuals, including so
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thought to be a disciplinary offenc
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2.2.2 Tools used in Forensic Comput
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structure and behaviour. Winhex pro
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with it are important aspects of an
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An important question for each arte
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For this research it is necessary t
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2007], which assist in building eve
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and therefore he did not have priva
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data may be affected by the behavio
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thumbnail cache is implemented in f
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available for office documents; the
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future. It is possible to establish
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structure and syntax the user and s
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Identify existing file carving tech
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throughout this research. Within th
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corroborate the results. Time const
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4.2.1 Legal Constraints The law can
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to the evidence and to ensure any a
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To ensure the evidence is accurate
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evidence being extracted is crucial
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analyse human behaviour, it can sti
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4.3 Criteria for evaluating the evi
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In order to determine an artefact w
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5 The Structure and Behaviour of th
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the way data changes. The experimen
Page 87 and 88: 5.4 Default Installations This sect
Page 89 and 90: Figure 5-3: The structure of thumbn
Page 91 and 92: these can be identified by the addi
Page 93 and 94: The tEXt chunks contain the metadat
Page 95 and 96: holds information about sample dept
Page 97 and 98: Start of tEXt Chunk This tEXt chunk
Page 99 and 100: 00 00 00 2074 45 58 7453 6F 66 74 @
Page 101 and 102: order to establish if the software
Page 103 and 104: Each piece of software installed by
Page 105 and 106: which is present in the subrecords
Page 107 and 108: 5.6.2 The modification of subrecord
Page 109 and 110: ascertain if unused subrecords woul
Page 111 and 112: in thumbnail view. This shows that
Page 113 and 114: 5.9.1 Metadata There are three dist
Page 115 and 116: only information which does not con
Page 117 and 118: information in the .thumbnails cach
Page 119 and 120: uses substantially more checks whic
Page 121 and 122: any manipulation to appear as stand
Page 123: highlighting the need for understan
Page 126 and 127: elationship between information con
Page 128 and 129: document the state of a default Win
Page 130 and 131: Figure 6-1: Directory structure for
Page 132 and 133: Clone 1-8: Directories at level 0 w
Page 134 and 135: Figure 6-2: The centralised thumbna
Page 136 and 137: Start of Record 87 F7 6A 62 4B 7B C
Page 140 and 141: Start of subrecord 14F8CE010 43 4D
Page 142 and 143: 6.5 Identifying the behaviour The t
Page 144 and 145: greater than the maximum size image
Page 146 and 147: experiment was repeated with a non-
Page 148 and 149: to be shown [Douglas, 2009].Figure
Page 150 and 151: 6.5.1.2 Circumstances where informa
Page 152 and 153: thumbnail cache based solely upon t
Page 154 and 155: the cache to remove inactive record
Page 156 and 157: 6.6.1 Windows.edb The database for
Page 158 and 159: Figure 6-10: Identifying the Defaul
Page 160 and 161: thumbnail view for 30 seconds. Upon
Page 162 and 163: checks are performed on the associa
Page 164 and 165: showing a relationship between info
Page 166 and 167: The type of a file can be identifie
Page 168 and 169: The event timeline created could th
Page 170 and 171: 6.9.2 Media thumbnails In Windows 7
Page 172 and 173: the provenance of artefacts. This i
Page 174 and 175: 6.10.2 Interpretation of Results An
Page 176 and 177: however it is still possible to tam
Page 178 and 179: implementations of the thumbnail ca
Page 180 and 181: valid results only when the file is
Page 182 and 183: 7.3.1 Statistical Methods If docume
Page 184 and 185: ate for HTML and JPEG files [Veenma
Page 186 and 187: Having described current methods fo
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previous experiments or downloaded
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L2: The fragment is part of a visua
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Table 7-1: Breakdown of file fragme
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approximately half the data in Data
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Table 7-3: A list of thumbnail cach
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Figure 7-2: Classifications for thu
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7.7.2 H2 For the identification of
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Relative offset: 48 0B 09 0C 11 0F
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The Bayesian Network takes into acc
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Figure 7-3: Bayesian network for H1
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Actual Fragment Type(Percentage) 7.
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Actual Fragment Type(Percentage) Ta
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Table 7-19: Method 4 Results for th
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more suited to pattern recognition
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and 2. This is possible because the
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This chapter has successfully ident
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8.2 Problem Definition In the intro
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information to examine at the end o
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files is described on the Joint Pho
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were not from thumbnail cache files
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In order to identify potential H3 f
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Actual Fragment Type (Percentage) p
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Figure 8-3: A summary of the hybrid
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cache file fragments. The headers i
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follow the standard PNG specificati
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then be viewed by an analyst and us
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Actual Fragment Type (Percentage) T
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8.8 Discussion The end aim of Chapt
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identification method into stages l
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9 Thumbnail cache fragment reassemb
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Once the fragments have been identi
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9.3.2 Logging In order to maintain
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H1:Thumbcache_idx.db file H2: Image
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Therefore this research assumes tha
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ecords and 2 partial records. The n
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equirement for generating table siz
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100% success rate, with 0% false po
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then stored and marked as a complet
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Once a start of file fragment has b
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number of fragments which contain o
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Figure 9-7: Reassembling an image b
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As the number of fragments being an
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file fragment identification on sto
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Linux Category_4: The last fragment
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Table 9-1: Results from reassembly
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activity. All the non-standard subr
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which substantially reduces the inf
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10 Establishing the evidential valu
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The thumbnail cache artefact extrac
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and 6. Each stage of the method has
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adapted to extract artefact from ot
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10.7 Discussion Both live system an
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10.8 Conclusion This chapter evalua
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Figure 11-1: A breakdown of aim of
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analysing the file type it is possi
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singular file fragment; by combinin
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processing time of the reassembly m
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In Chapter 9.5 a decision was taken
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12 Conclusions and future work 12.1
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potential for improving the identif
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installations of the operating syst
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Carnagey, N.L., Anderson, C.A. & Bu
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Facebook, 2013. Facebook. Available
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Helix, 2011. Helix. Available at: h
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Noblett, M., Pollitt, M., Presley,
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Stone-kaplan, K., Roter, M., 2003.
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APPENDICES Cranfield University | 3
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A.1.3 Image File Header typedefstru
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Appendix B Bayesian probability tab
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B.8 Fragment contains the ASCII str
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B.15 32 byte record structure SR po
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B.19 H3 Each byte frequency is less
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B.21 H5 Stored in valid PNG chunks
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Appendix C Peer Reviewed Publicatio
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Cranfield University | 327
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