# Presentation: 658502

## Computer Forensics Tool Testing at NIST

**Jim Lyle **
**Information Technology Laboratory**
**Phone: (301) 975-3207**
**E-mail: **_[JLYLE@NIST.GOV](mailto:JLYLE@NIST.GOV)_
**WWW: http://www.cftt.nist.gov**

**Notes:**
It is my pleasure to be here with you today to describe some of the significant work ongoing at NIST involving information technology and the fairly new concept of computer forensics.
NIST is attempting to introduce science into the computer forensics arena by basing our work on first principles of computer science, accepted practice, peer review, and publication of results. <click>

## Computers &The Internet

- Marvelous tools
- Improve quality of life
- Enable global communication
- Improve productivity
- Makes many activities easer, faster, ...
- ... even criminal activity

## A Shocking Revelation . . .

- Computers can be involved in crime ...
- As a victim
- As a weapon
- As a witness
- As a record
- As contraband

**Notes:**
This is the hook. The expected audience is technical but not law enforcement.

## Outline of an Investigation

- Get proper authorization
- Seize evidence (Hard drives, floppies ...)
- Create duplicates for analysis
- Analyze the duplicates
- Exclude known benign files
- Examine obvious files
- Search for hidden evidence
- Report results

**Notes:**
Why do we care about hard drives so much. Central to the integrity of the investigation.

## Investigators Need ...

- Computer forensic investigators need tools that ...
- Work as they should
- Produce results admissible in court

**Notes:**
Explain why there is a problem.

## Admissible Results

- Software tools must meet Daubert criteria
- Tested: accurate, reliable & repeatable
- Peer reviewed
- Generally accepted methodology

**Notes:**
Explain why there is a problem.

## Response to Problem

- Independent testing of forensic tools
- Public review of results
- Apply black box testing theory to tools

## Goals of CF at NIST

- Establish methodology for testing computer forensic tools (CFTT)
- Provide international standard reference data that tool makers and investigators can use in an investigations (NSRL)

## Why NIST/ITL is involved

**Mission: Assist federal, state & local agencies**
**NIST is a neutral organization – not law enforcement or vendor**
**NIST provides an open, rigorous process**

## Project Sponsors

- NIST/OLES (Program management)
- NIJ (Major funding)
- FBI (Additional funding)
- DOD (Equipment and support)
- Homeland Security (Technical input)
- State & Local agencies (Technical input)

## Project Tasks

- Identify forensics functions e.g.,
- Disk imaging,
- Hard drive write protect,
- Deleted file recovery
- String searching
- Develop specification for each function
- Peer review of specification
- Test methodology for each function
- Test Tools (by function) & Report results

**Notes:**
Ok now how are we going to do things. The plan ...

## Current Activities

- Hard drive imaging tools
- Software hard drive write protect
- Hardware hard drive write protect
- Deleted file recovery
- String Searching

## Challenges

- No standards or specifications for tools
- Arcane knowledge domain (e.g. DOS, Windows drivers)
- Reliably faulty hardware
- Many versions of each tool

**Notes:**
What are the hard things to do. Where can NIST help?

## Overview of Methodology

- CFTT directed by Steering Committee
- Functionality driven
- Specifications developed for specific categories of activities, e.g., disk imaging, hard drive write protect, etc.
- Test methodology developed for each category

## Developing a Specification

- After tool function selected by SC ...
- Focus group (law enforcement + NIST) develop tool function specification
- Spec posted to web for public comment
- Comments incorporated
- Develop test environment

## Tool Test Process

- After SC selects a tool ...
- Acquire tool & review documentation
- Select test cases
- Execute test cases
- Produce test report

## Disk Imaging Test Parameters

| Parameter | Value |
| --- | --- |
| Functions  | Copy, Image, Verify  |
| Source interface  | BIOS to IDE, BIOS to SCSI, ATA, ASPI, Legacy BIOS |
| Dst interface  |  |
| Relative size | Src=Dst, Src<Dst, Src>Dst |
| Errors | None, Src Rd, Dst Wt, Img R/W/C |
| Object type | Disk, FAT12/16/32, NT, Ext2 |
| Remote access | Yes, no |

## Capabilities to test disk imaging

- Accuracy of copy
- Compare disks
- Initialize disk sectors to unique content
- Verify source disk unchanged
- Corrupt an image file
- Error handling: reliably faulty disk

## Test Case Structure: Setup

- 1.     Record details of source disk setup.
- 2.     Initialize the source disk to a known value.
- 3.     Hash the source disk and save hash value.
- 4.     Record details of test case setup.
- 5.     Initialize a destination disk.
- 6.     If the test requires a partition, create and format a partition on the destination disk.
- 7.     If the test uses an image file, partition and format a disk for the image file.

## Test Case Structure: Run Tool

- If required, setup I/O error
- If required, create image file
- If required, corrupt image file
- Create destination

## Test Case Structure: Measure

- Compare Source to Destination
- Rehash the Source

## Test Logging

- Log everything, automatically if practical
- Hardware, Software, Versions
- Time/date
- Operator

## Legacy BIOS Quirks

- Some may under report drive size
- Example, Quantum SIROCCO1700A has 3335472 sectors 3309/16/63 spc 1008
- BIOS: 3,330,432 sectors with geometry 826/64/63 spc 4032
- BIOS under reports by 1.25 logical cyls and 5 physicals

## Evaluating Test Results

- If a test exhibits an anomaly ...
- Look for hardware or procedural problem
- Anomaly seen before
- If unique, look at more cases
- Examine similar anomalies

## Refining the Test Procedure

- During **dd** testing some results seemed to indicate that the Linux environment was making a change to the source disk.
- After investigation we found that the problem was actually the test procedure.

## Hard Drive Write Protect

- Can be done either in hardware or software
- Software write protection limited to specific environment: BIOS access or device driver
- Hardware write protection more general

## Hard Drive BIOS Access

## SWB Tool Operation

## Test Harness Operation

## HWB Testing

- Device

- Send I/O CMD to Device

- Return result to CPU

- BUS1

- BUS 2

- PROTOCOL
-  ANALYZER

- Monitor Bus Traffic

- BUS

- HWB Testing

- HWB

## Impact

- Release 18 (Feb 2001) - A US government organization was doing some testing and uncovered an issue under a specific set of circumstances.
- Linux doesn’t use the last sector if odd
- Several vendors have made product or documentation changes
- CFTT cited in some high profile court cases

## Available Specifications

- Hard Drive Imaging (e.g., Safeback, EnCase, Ilook, Mares imaging tool)
- Write Block Software Tools (e.g., RCMP HDL, Pdblock, ACES)
- Write Block Hardware Devices (A-Card, FastBlock, NoWrite) – not final

## Specifications Under Development

- String Searching
- Deleted File Recovery
- Revised Disk Imaging

## Available Test Reports

- Sydex SafeBack 2.0
- NTI Safeback 2.18
- EnCase 3.20
- GNU dd 4.0.36 (RedHat 7.1)
- FreeBSD 4.4 dd
- RCMP HDL V0.8

## Test Reports in Production

- RCMP HDL V0.4
- RCMP HDL V0.5
- RCMP HDL V0.7

## Available Testing Software

- FS-TST – tools to test disk imaging: drive wipe, drive compare, drive hash (SHA1), partition compare. (DCCI uses these tools)
- SWBT – tools to test interrupt 13 software write blockers

## Benefits of CFTT

- Benefits of a forensic tool testing program
- Users can make informed choices
- Neutral test program (not law enforcement)
- Reduce challenges to admissibility of digital evidence
- Tool creators make better tools

**Notes:**
Why NIST? What are the Goals?

## Contacts

- Jim Lyle				Doug White
- www.cftt.nist.gov			www.nsrl.nist.gov
- cftt@nist.gov				nsrl@nist.gov
- Mark Skall
- Chief, Software Diagnostics & Conformance Testing Div.
- www.itl.nist.gov/div897		skall@nist.gov
- Sue Ballou, Office of Law Enforcement Standards
- Steering Committee Rep. For State/Local Law Enforcement
- susan.ballou@nist.gov