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Introduction to IT Forensic Technology and IT Security

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Introduction to IT Forensic Technology and IT Security Introduction to IT forensic technology and IT security Partitions and files AccessData FTK Imager and FTK (Forensic ToolKit) Digital investigator knowledge and skills Logga bevis med forensiska verktyg • AccessData FTK (Forensic Tool Kit) och de flesta andra forensiska tool kit (se lista senare) har funktionalitet för – Rapport av undersökningen och loggning av information – Återskapa raderade filer och inbäddade filer i filer – Hitta data/filer i slack-space och free-space – Carving för att hitta data och filer – Olika typer av filsystem – Rapporter om funna filer på disken och deras hash – Filtypsanalyser av header (filer med fel filsuffix) – Time-lines för filer i systemet – Mycket mera… • Verktygens kostnad är från fria -> mycket dyra Sorterade filer efter indexering av ett case (image) Track, sector and cluster Figure 1.1 FIGURE 15.5 A depiction of platters, tracks, sectors, clusters, and heads on a computer disk. ©2011 Eoghan Casey.Copyright Published © 2011 by Academic Elsevier Inc.Press All Inc. rights reserved. LBA (Logical Block Addressing) • LBA, kallas även Linear Base Address Platter Model – Är den vanligaste adresserings metoden • Cylinder-Head-Sector (CHS) schema • LBA har 48 bits adressering – Geometri translation i BIOS – 128 pebibyte (PiB, 2^50) om 512 byte sektorer används Beginning End LBA=0 Linear Model Index=i Beginning End DOS/MBR Partitioner VBR (Volume Boot Record) Figure 1.1 FIGURE 15.6 Simplified depiction of disk structure with two partitions, each containing a FAT formatted volume. ©2011 Eoghan Casey.Copyright Published © 2011 by Academic Elsevier Inc.Press All Inc. rights reserved. DOS/MBR Partitioner • Partitionsinformationen är alltid lagrad på cylinder 0, head 0, sector 1 (sector 0 i vissa program) dvs. den första sektorn • Master Boot Record (MBR) – de första 512 byten File System Forensic Analysis - Brian Carrier MBR 446-509 Locical disk? Physical disk? Endianness http://en.wikipedia.org/wiki/Endianness • Byte och bit ordningen för att representera data • Little endian – Intel x86, LSB at lowest adress • Big endian – Motorola, MSB at lowest adress • Bi endian – I princip alla andra processorarkitekturer - inställningsbar – ARM, MIPS, SPARC, IA64 etc. Word • Word exempel – 0x39 LE Data 6 9 3 5 – 0x93 BE Adress 0x1023 0x1024 0x1025 0x1026 DOS/MBR Partitioner • Disk/partition parameters 446 - 509 • 4 primary partitions can be created on DOS disks – Boot code points to VBR (Volume Boot Record) or Boot sector File System Forensic Analysis - Brian Carrier Big Endian = 0x00 = 0x000101 = 0x07 = 0x63BFFE = 0x0000003F = 63 = 0x00960525 = 98311717 Tolkning av ett 16 byte partition entry – omvandla LE word till BE byte-index och läs som LE eller BE 1 0 3 2 5 4 7 6 9 8 11 10 13 12 15 14 Några DOS Partition typer DiskExplorer MBR Formatering av diskar http://support.microsoft.com/?kbid=302686 • Quick format (Windows) – Tar bara bort FAT/MFT (File Allocation Table)/(Master File Table) – Allt annat är kvar på disken • Regular format (Windows) – Som quick format men scannar även efter bad sectors • ”Low level format” utility från disktillverkare – Gör write-read verify och andra kontroller av disken • ”Low level format” från fabrik – Servo, sector layout, defect management etc. – Håller för diskens livstid, kan inte göras om • Återställa MBR – odokumenterat kommando – FDISK /MBR (DOS/Windows) • VISTA/7 från Windows RE (Recovery Environment) – bootrec /FixMbr och bootrec /FixBoot Create a bit-stream image 1 Hårdvaru skrivskydds device • DOS - diskcopy – a:\>diskcopy [drive1] [drive2] /V • Linux – dd (disk dumper?) – http://en.wikipedia.org/wiki/Dd_(Unix) – dd if=/dev/floppy of=/evidence/floppyImage.dat – Paramatrar: bs=4096 conv=noerror count=1 Create a bit-stream image 2 File end File start File end File start Figure 1.1 FIGURE 16.4 Comparing bitstream copying to regular copying. ©2011 Eoghan Casey.Copyright Published © 2011 by Academic Elsevier Inc.Press All Inc. rights reserved. File size Sector border Cluster border Sectors are usually 512 byte, which is the smallest writable size - clusters Figureare usually1.1 4 kB in size FIGURE 17.4 Diagram of file with a logical size that is larger than its valid data length, leaving uninitialized space. ©2011 Eoghan Casey.Copyright Published © 2011 by Academic Elsevier Inc.Press All Inc. rights reserved. Söka efter data i slack space “Cluster level searching” • Kallas även för file carving (datacarve i accessdata) • Söker igenom hela disken på byte nivå inklusive boot sektor, icke allokerad disk, slack space… ALLT! • Hittade filer eller fragment av filer kan sparas till nya filer i caset – Gamla raderade filer eller filer som finns inbäddade i andra filer • Sökverktyget måste ha stöd för och kunna identifiera både HEX, ASCII och Unicode tecken m.m. • Långsammare än ”content level searching” • Går ut på att söka efter textsträngar och efter fil- headers och footers • Man måste i stort sett veta vad man letar efter om inte bra stöd finns i verktyget – Scalpel är ett bra verktyg, härstammar från Foremost – TestDisk & PhotoRec File mangling • Är konsten att modifiera en fil för att dölja innehållets format - i syfte försvåra att rätt applikation kan använda filen – Analysera filens suffix, header signatur och format • Tusentals format existerar! – http://www.webopedia.com/quick_ref/fileextensions.asp eller http://filext.com/ – http://www.wotsit.org - programmer's file and data format resource • File mangling metoder – Ändra filens suffix – Ändra filens association i registret • Ikonen för filen ändras • Rätt program startar inte som default Inspektera filheaders för signaturer • Om tveksamhet förekommer ang. suffix inspektera med hex editor • De flesta filer har en unik signatur – .dll, .sys, .ocx, .drv, .exe och några till börjar med ”MZ” eller 4D5A i hex – Grafiska filer brukar ha suffixet med i headern • Att inspektera många filer är inget litet jobb – Görs automatiskt i forensiska verktygen • AccessData – Outside In Technology från Stellent – Man kan göra ett eget script eller program för detta ganska lätt – Technology Pathways har en signaturlista de tagit fram tillsammans med Harlan Carvey Image-format • Format som har extra info, t.ex. EWF • Unix/Linux dd (raw) format Källa: afflib.org FTK Imager image-format • FTK imager kan skapa – Raw dd – SMART – Encase • FTK imager läser FTK imager gränssnitt Interpreters Other time decoders http://www.digital-detective.co.uk/ Figure 1.1 FIGURE 16.9 Forensic date and time decoder. These times are generally GMT and must be adjusted for time zones. ©2011 Eoghan Casey.Copyright Published © 2011 by Academic Elsevier Inc.Press All Inc. rights reserved. Drive Freespace När FTK Imager hittar en kontinuerlig “klump” med ledig diskyta (unallocated space) så namnger den och identifierar ytan med det kluster den börjar med Nedan kan vi se en 262140 KB klump som börjar på kluster 3 och en annan 2624 KB klump som börjar på kluster 65790 osv. Exporting Files / Folders Hash Values Results in a CSV file Acquisition Verification Encase / DD ?? Verified based on image format News in FTK imager 3.x News in FTK imager 3.x Tekniker att gömma data • Det finns många sätta att gömma data på, de mest kända – Raderade filer? (ett specialfall) – Hidden file attribute – Alternate Data Streams (ADS) – Steganografi – Slack space/ej allokerade kluster – File mangling – Ofta spenderas en stor del av tiden i en forensisk undersökning inom detta område • Krävande och tidsödande men samtidigt intressant Gömda filer • Attrib +h kommandot • Show hidden files option i explorer • Det finns normalt sett många gömda filer i ett system – Malware eller normalt? • Explorer är inte optimal – HFind från Foundstone är bättre • Linux/Unix/Mac – Filer som börjar med ’.’ Carving for files http://www.datalifter.com http://www.cgsecurity.org/wiki/PhotoRec Figure 1.1 FIGURE 17.9 DataLifter being used to carve files from two blobs of unallocated space and one blob of file slack from a system. ©2011 Eoghan Casey.Copyright Published © 2011 by Academic Elsevier Inc.Press All Inc. rights reserved. FTK Interface Menu Commands Toolbars Overview Tab Explore Tab Graphics Tab E-Mail Tab Search Tab Bookmark Tab FTK Case Files <casename>.ftk Creating a New Case New Case Information Examiner Information Case Log Options Process Options Refining Case Evidence Defining Index Parameters Selecting Case Evidence Evidence Information FTK Time Zone Settings • FTK requires selection of a time zone for any FAT volume • FAT times are converted to GMT in the case database o FAT vs. NTFS • Removable Media o Should get the settings of associated computers if they exist o Use local settings if they do not Setup Completion AccessData Registry Viewer Password Recovery ToolKit Manage Profiles... Dictionary Tools... Right or double click to get more properties and information about the recovery job Note! May need to be started as admin DI - ”mjuka” färdigheter • Undersökande/analyserande färdigheter – Logisk • Effektiv vid interaktion med människor, ”social förmåga” att kunna ”ta” människor – Behövs vid intervjuer med vittnen och brottslingar • Skriva och kommunicera – Måste kunna förklara så alla förstår och skriva/dokumentera på ett professionellt sätt • Objektivitet och professionalism – Bevis kan svänga om till den misstänktes fördel – Omsorg om detaljer är en nyckelfaktor – Förbli fokuserad på fakta DI tekniska färdigheter 1 • En DI använder ofta mycket tekniskt avancerade specialverktyg – Operativsystemets verktyg och egenskaper, script • Time, date, events, loggar, tasklist … etc. – Windows
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