The Autopsy Forensic Browser is a graphical interface to the command line digital investigation analysis tools in The Sleuth Kit. Together, they can analyze Windows and UNIX disks and file systems (NTFS, FAT, UFS1/2, Ext2/3).
The Sleuth Kit and Autopsy are both Open Source and run on UNIX platforms. As Autopsy is HTML-based, you can connect to the Autopsy server from any platform using an HTML browser. Autopsy provides a “File Manager”-like interface and shows details about deleted data and file system structures.
A dead analysis occurs when a dedicated analysis system is used to examine the data from a suspect system. In this case, Autopsy and The Sleuth Kit are run in a trusted environment, typically in a lab. Autopsy and TSK support raw, Expert Witness, and AFF file formats.
A live analysis occurs when the suspect system is being analyzed while it is running. In this case, Autopsy and The Sleuth Kit are run from a CD in an untrusted environment. This is frequently used during incident response while the incident is being confirmed. After it is confirmed, the system can be acquired and a dead analysis performed.
Evidence Search Techniques
- File Listing: Analyze the files and directories, including the names of deleted files and files with Unicode-based names.
- File Content: The contents of files can be viewed in raw, hex, or the ASCII strings can be extracted. When data is interpreted, Autopsy sanitizes it to prevent damage to the local analysis system. Autopsy does not use any client-side scripting languages.
- Hash Databases: Lookup unknown files in a hash database to quickly identify it as good or bad. Autopsy uses the NIST National Software Reference Library (NSRL) and user created databases of known good and known bad files.
- File Type Sorting: Sort the files based on their internal signatures to identify files of a known type. Autopsy can also extract only graphic images (including thumbnails). The extension of the file will also be compared to the file type to identify files that may have had their extension changed to hide them.
- Timeline of File Activity: In some cases, having a timeline of file activity can help identify areas of a file system that may contain evidence. Autopsy can create timelines that contain entries for the Modified, Access, and Change (MAC) times of both allocated and unallocated files.
- Keyword Search: Keyword searches of the file system image can be performed using ASCII strings and grep regular expressions. Searches can be performed on either the full file system image or just the unallocated space. An index file can be created for faster searches. Strings that are frequently searched for can be easily configured into Autopsy for automated searching.
- Meta Data Analysis: Meta Data structures contain the details about files and directories. Autopsy allows you to view the details of any meta data structure in the file system. This is useful for recovering deleted content. Autopsy will search the directories to identify the full path of the file that has allocated the structure.
- Data Unit Analysis: Data Units are where the file content is stored. Autopsy allows you to view the contents of any data unit in a variety of formats including ASCII, hexdump, and strings. The file type is also given and Autopsy will search the meta data structures to identify which has allocated the data unit.
- Image Details: File system details can be viewed, including on-disk layout and times of activity. This mode provides information that is useful during data recovery.
- Case Management: Investigations are organized by cases, which can contain one or more hosts. Each host is configured to have its own time zone setting and clock skew so that the times shown are the same as the original user would have seen. Each host can contain one or more file system images to analyze.
- Event Sequencer: Time-based events can be added from file activity or IDS and firewall logs. Autopsy sorts the events so that the sequence of incident events can be more easily determined.
- Notes: Notes can be saved on a per-host and per-investigator basis. These allow you to make quick notes about files and structures. The original location can be easily recalled with the click of a button when the notes are later reviewed. All notes are stored in an ASCII file.
- Image Integrity: It is crucial to ensure that files are not modified during analysis. Autopsy, by default, will generate an MD5 value for all files that are imported or created. The integrity of any file that Autopsy uses can be validated at any time.
- Reports: Autopsy can create ASCII reports for files and other file system structures. This enables you to quickly make consistent data sheets during the investigation.
- Logging: Audit logs are created on a case, host, and investigator level so that actions can be easily recalled. The exact Sleuth Kit commands that are executed are also logged.
- Open Design: The code of Autopsy is open source and all files that it uses are in a raw format. All configuration files are in ASCII text and cases are organized by directories. This makes it easy to export the data and archive it. It also does not restrict you from using other tools that may solve the specific problem more appropriately.
- Client Server Model: Autopsy is HTML-based and therefore you do not have to be on the same system as the file system images. This allows multiple investigators to use the same server and connect from their personal systems.
A sample acreen shot of Autopsy in action: