COMP 4027 Forensic and Analytical Computing

ANTIFORENSICS - Accidental: when technology and circumstance hinder the forensic analyst

In this section, we look at "accidental" antiforensics which generally arise as a side effect of something else, and are not deliberately intended to defy forensic examinations but have the same effect nevertheless.

Accidental loss through mishandling

One of the problems we have heard of from guest speakers is that it is important to not contaminate the data when handling it, as this contamination will render the data not useful for evidence purposes. This could happen even through merely starting up a device since even a startup records information such as last use or access times and dates.

This data contamination could consist of inserting new information (such as websites on a log) or overwriting prior data.

Technology

We have also heard how the proliferation of devices had led to a proliferation of operating software, so that forensic analysts now need to have some ability to examine a much wider range of devices and systems than in any time previously.

This proliferation of devices and software implies a concomitant expansion of analysis tools. Where these tools exist, they invariably have some cost asociated with them. however the proliferation of devices and systems also means that there are often no such tools available, at least not yet. We also need to know that the vendor of any such tool is accredited.

Another byproduct of technological advances is the massive increase in storage capacity, giving more disc space to inspect, slowing down imaging.

Also the availablilty of cheap storage encourages people to make more backups over new devices and media.

All of these have the effect of significantly increasing the workload of the forensic analyst, as we saw in Rob's guest lecture a few weeks back.

Off-site storage and third-party data

Some sources of data are difficult to procure. A forensic analysis of a hard disc is relatively accessible and the procedures well-established. However Web 2.0 allows users to store their private or shared resources separately from their personal computers and devices, and retrieving this information without compliance of the user can be problematic.

This "off-site" storage is manifested in Web hosting services, shared document services (such as GoogleDocs), peer-to-peer, and even in mail services (gmail and hotmail). There have been some privacy concerns with these services, sometimes due to software errors. However the agencies hosting these services are able to collect a significant quantity of personal information.

These sharing services allow users to do at a remote site what would previously have been done on a file kept on their local hard disc. Getting a copy of that file for analysis might depend on finding a cached copy.

A lot of evidence is also contained in records held by third parties. This includes web logs, query logs, site accesses, banking or commercial records. While law enforcement agencies can sometimes successfully access such data through a court order, this option is not open to industrial forensics analysts.

Even when data is accessible, it can comprise an enormous quantity of information. For example, web logs can yield up information on a target's interests, complete with date and downloaded data. However an analyst ends up having to sift through large numbers of entries, most of which are relatively anonymous.

A similar issue occurs with intelligence agencies who collect very large quantities of data (perhaps the entire traffic via US servers?). It is not feasible for all intercepted materials to be inspected by a human agent, as it had been for example at Bletchley Park during WWII. Instead, intercepted data is purportedly text-analysed with keyword searches

Forensics?

The technology and the mishandling problems can all be managed to some extent, through a process of training and investment in forensics.

However some of the problems cannot easily be addressed with technical solutions. Distributed storage is difficult to deal with since ISPs are not always willing to hand over their logs for analysis, (Google for example refusing to hand over their web logs to law enforcement agencies).

In our next section, our guest speaker from SAPOL will be discussing some of these issues, in particular how to deal with "cloud computing",


Last update hla 2009-05-17