CSN11121/CSN11122 System Administration and Forensics Introduction to Digital Forensic 20/10/2011

Lecture Objectives 1.History and definition of Digital Forensics 2.Context for an investigation 3.An overview of the main theoretical concepts 4.Storage Devices 5.Partitions

Recommended Reading 1.B Carrier, File System Forensic Analysis, March , Addison-Wesley Professional 2.H Carvey, Windows Forensic Analysis DVD Toolkit, 11th June 2009, Syngress 3.C Pogue, Unix and Linux Forensic Analysis DVD Toolkit, 30th June 2008, Syngress 4.M.E. Russinovich and D.A. Solomonm, Windows Internals 5th Edition, 7th January 2009, Microsoft Press (chapter 1 to chapter 3) 5.K.J. Jones, Real Digital Forensics, 3rd October 2005, Addison-Wesley Professional

Online Resources Digital Forensic Research Workshop (DFRWS) – – Challenges – Projects National institute of Standards and technology (NIST) – Journal - Digital Investigation – Forensics Wiki –

DIGITAL FORENSICS

It is impossible for the criminal to act, especially considering the intensity of a crime, without leaving traces of his presence. - Edmond Locard

With contact between two items, there will be an exchange - Locard’s exchange principle

Computer Forensics 1984 – Scotland Yard: Computer Crime Unit – FBI computer forensics departments 1990 – Computer Misuse Act (CMA)

Digital Forensics The use of scientifically derived and proven methods towards the preservation, collection, validation, identification, analysis, interpretation, documentation, and presentation of digital evidence derived from the digital sources for the purpose of facilitation or furthering the reconstruction of events found to be criminal, or helping to anticipate unauthorized actions shown to be disruptive to planned operations. - Digital Forensics Research Workshop

Investigative Context Primary Objectives Secondary Objectives Environment Law EnforcementProsecutionPost-Mortem Military IW Ops Continuity of Operations Prosecution Real-Time/Post- Mortem Business and Industry Continuity of Service Prosecution Real-Time/Post- Mortem

Digital Investigation A digital investigation is a process where we develop and test hypotheses that answer questions about digital events. This is done using the scientific method where we develop a hypothesis using evidence that we find and then test the hypothesis by looking for additional evidence that shows the hypothesis is impossible. Digital Evidence is a digital object that contains reliable information that supports or refutes a hypothesis. - B. Carrier, 2006 File System Forensic Analysis,

Static vs. Live Traditional Static Investigations – Hard disk or some other form of static resource – Data at a resting state – Able to image, return to original source and conduct further analysis Live investigation – Occurs when the machine is running

Volatile Investigations Has impact on device under investigation Not repeatable Does not fit in with classic forensic investigative models OS must be trusted New questions cannot be asked later

Investigation Process Acquisition – Preservation – Collection – Verification Analysis – Search for evidence – Hypothesis Creation – Confirm or refute hypothesis with evidence Presentation – Report the findings of the investigation – Objective manner

Characteristics of Evidence 1.Data can be viewed at different levels of abstraction 2.Data requires interpretation 3.Data is Fragile 4.Data is Voluminous 5.Data is difficult to associate with reality

Characteristics of Evidence 1.Data can be viewed at different levels of abstraction 2.Data requires interpretation 3.Data is Fragile 4.Data is Voluminous 5.Data is difficult to associate with reality

Characteristics of Evidence 1.Data can be viewed at different levels of abstraction 2.Data requires interpretation 3.Data is Fragile 4.Data is Voluminous 5.Data is difficult to associate with reality

Characteristics of Evidence 1.Data can be viewed at different levels of abstraction 2.Data requires interpretation 3.Data is Fragile 4.Data is Voluminous 5.Data is difficult to associate with reality

Characteristics of Evidence 1.Data can be viewed at different levels of abstraction 2.Data requires interpretation 3.Data is Fragile 4.Data is Voluminous 5.Data is difficult to associate with reality

Best Practice ACPO – Principle 1 - No action taken by law enforcement or their agents should change data held on an electronic device or media which may subsequently be relied upon in Court. – Principle 2 - In exceptional circumstances where a person finds it necessary to access original data held on an electronic device or media, that person must be competent to do so, and be able to give evidence explaining the relevance and the implications of their actions.

Best Practice ACPO – Principle 3: An audit trail or other record of all processes applied to computer based electronic evidence should be created and preserved. An independent third party should be able to examine those processes and achieve the same result.

Best Practice ACPO – Principle 4: The person in charge of the investigation (the case officer) has overall responsibility for ensuring that the law and these principles are adhered to.

Tools 1 st Generation – Command Line, Task oriented, Act on original data 2 nd Generation – GUI interface, capable of making copies, multi- functional 3 rd Generation – Work on distributed systems and live systems – Live… ?

Tool Characteristics Verifiable - Can it be shown to behave within certain bounds of behaviour? Reproducibility - Can a tool produce results which are reproducible? Non-interference - Are the results obtained with a tool that has open source code, and thus does not contain obfuscated code? Usability - Can the tool help the investigator review and make decisions about the layer of abstraction being viewed? Comprehensive - Can the tool allow the investigator access the data output of the tool at any given level of abstraction?

Future Research Challenges facing the investigation community – S.L. Garfinkel, Digital forensics research: The next 10 years, Digital Investigation, vol. 1, no. 7, pp , 2010 – “The coming Digital Forensics Crisis”

Challenges Size of storage devices Embedded flash devices Proliferation of operating systems and file formats Multi-device analysis Pervasive Encryption Cloud computing RAM-only Malware Legal Challenges decreasing the scope of forensic investigations

STORAGE DEVICES & PARTITIONS

Required Reading D. Byers, N. Shahmehri, “Contagious errors: Understanding and avoiding issues with imaging drives containing faulty sectors”, Digital Investigation, no. 5, pp. 29 – 33, 2008 A.Jones, C. Meyler, “What Evidence is left after disk cleaners?”, Digital Investigation, no. 1, pp. 183 – 188, 2004 B.J. Nikkel, “Forensic Analysis of GPT disks and GUID partition tables”, Digital Investigation, no.6, pp , 2009

Required Reading M. Belford, “Methods of discovery and exploration of Host Protected Ares on IDE storage devices that conform the ATAPI-5”, Digital Investigation, no.2, pp , 2006 K. MacDonald, “To Image a Macintosh”, Digital Investigation, no. 2, pp , 2006 J. R. Lyle, “A strategy for testing hardware write block devices”, Digital Investigation, no. 3, pp. 3-9, 2006

Storage Media Hard disks, floppy disk, thumb drives etc. Hard disks are the richest in digital evidence Integrated Disk Electronics (IDE) or Advanced Technology Attachment (ATA) Higher performance SCSI drives Fireware is an adaptation of SCSI standards that provides high speed access to a chain of devices All hard drives contain platters made of light, rig-hid material such aluminum, ceramic or glass

More on Hard Drives – Platters have a magnetic coating on both sides and spin between a pair of read/write heads – These heads move like a needle on top of the old LP records but on a cushion of air created by the disk above the surface – The heads can align particles of magnetic media called writing, and can detect how the magnetic particles are assigned – called reading – Particles aligned one way are considered “0” and aligned another way “1”

Hard Disks cc by-sa, Cambridge Cat/Anna, flickr.com Platters Spindle Head Actuator Arm

Storage Cylinders are the data tracks that the data is being recorded on Each track/cylinder is divided into sectors that contain 512 bytes of information – 512*8 bits of information Location of data can be determined by which cylinder they are on which head can access them and which sector contains them or CHS addressing Capacity of a hard drive # of C*H*S*512

Hard Disk Platters

Tracks and Sectors Track Sector (512bytes)

Tracks and Sectors Track #0 Track #1, Sector #7

Storage Characteristics Volatility – Non-Volatile – Volatile Mutability – Read/Write – Read Only – Slow Write, Fast Read Storage Accessibility – Random Access – Sequential Access Addressability – Location – File – Content

CHS Values 16-bit Cylinder value (C) 4-bit Head Value (H) 8-bit Sector Value (S) Old BIOS: – 10-bit C – 8-bit H – 6-bit S – Limited to 528MB disk

Logical Block Address (LBA) LBA address may not be related to physical location of data Overcomes the 8.1 GB Limitation of CHS Plug old CHS values into: LBA = (((CYLINDER * heads_per_cylinder) * HEAD) * sectors_per_track) + SECTOR -1 E.g. CHS 0,0,1 = LBA 0

Storage Volume

Volume vs Partition Volume – A selection of addressable sectors that can be used by an OS or application. These sectors do not have to be consecutive Partition – A selection of addressable sectors that are consecutive. By definition, a partition is a volume

Partition Analysis A Partition organises the layout of a volume Sector Addressing – Physical Address (LBA or CHS) – Logical Disk Volume Address – Logical Partition Volume Address

Sector Addressing B Carrier, File System Forensic Analysis, pp75

Partition Analysis Analyse Partition Tables – Process them to identify the layout – Can then be used to process partition accordingly – Determine the type of data inside the partition Perform a sanity check to ensure that the partition table is telling the truth This is important when imaging

Sanity Check B Carrier, File System Forensic Analysis, pp76

DOS Partitions Most commonly found with i386/x86 systems No standard reference Master Boot Record in first sector (1 st 512 byte) – Boot Code – Partition Table – Signature Value MBR Supports a maximum of 4 partitions

B Carrier, File System Forensic Analysis, pp 83

Partition Table Starting CHS Address Ending CHS Address Starting LBA Address Number of Sectors in Partition Type of Partition Flags Limitation – 2 Terabyte Disk Partition Limitation MBR Partition size field is 32 bits

Extended Partitions Limitation of 4 Primary Partitions Creation of 3 Primary Partitions and 1 primary extended partition Primary Extended partition uses a similar MBR layout in order to create a linked list of records, showing where each new extended partitions exists in relation to the start of the last

B Carrier, File System Forensic Analysis, pp 94

ANY QUESTIONS?