Going Dutch

Digital crime often puts the police under pressure. They don't have the staff to collect and analyze the volumes of digital evidence that often accompanies a large-scale investigation. At the same time, digital evidence is becoming increasingly important – data on mobile phones and computers belonging to suspects can provide circumstantial evidence and even hard facts. The Dutch police [1] developed the Open Computer Forensics Architecture (OCFA [2]) as an open source tool for professional criminal investigators. Dutch authorities use the modular OCFA framework for forensic investigations. The OCFA architecture is a combination of several existing forensic tools and libraries. OCFA splits the forensic process into two parts. First, specialists with knowledge of digital forensics extract content from hard disks and other devices. Then, criminal investigators use a simple web interface to analyze the data and look for evidence.

Installable OCFA 2.0.2 packages exist for Debian Etch, Ubuntu 5.10, and SUSE 9.3 and 10.1. The tarballs include OCFA RPMs or DEBs, along with a number of additional packages and installation guides, which also describe the packages you need to install manually up front. The current 2.1.0 version is available as a source package only. The creators of OCFA see the analysis process as a kind of digital data wash (Digiwash) and, therefore, install OCFA in the /usr/local/digiwash directory.

One of the biggest obstacles to forensic analysis is the sheer bulk of evidence. Investigators face the task of identifying incriminating material among hundreds of gigabytes of irrelevant data. But skipping files and directories just because the names sound nondescript is no solution either. Many forensic tools assist the investigator by performing automatic analysis and characterization of the identified files. Digiwash takes this idea one step further by running file to identify the file type. It then goes on to automatically analyze specific file types, thus saving the forensic investigator some of the grunt work. OCFA uses Lucene to index Microsoft Word files and other Office documents. The raw text is extracted by running antiword. PDF files are converted with pdftotext; mailwash extracts files and metadata from mailboxes. The developers have even devised a means for capturing the information in PGP keyrings, mapping the key IDs of signed and encrypted mail to clear text names. OCFA also groups photos and generates thumbnails.

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