Although the document is not intended to be a definitive manual of every single operation that may take place during an investigation, it does provide some first-rate guidance and advice. Interestingly, the thrust of the guide is about forensic procedures, rules of evidence and legal process, and is a great resource for anyone tasked with drafting incident response policies and procedures.

From the outset, I would like readers to note that when tasked (usually by the HR department) with conducting an investigation relating to computer equipment there are some key ‘rules’ to be followed:

Rule 1. An examination should never be performed on the original media.

Rule 2. A copy is made onto forensically sterile media. New media should always be used if available.

Rule 3. The copy of the evidence must be an exact, bit-by-bit copy. (Sometimes referred to as a bit-stream copy).

Rule 4. The computer and the data on it must be protected during the acquisition of the media to ensure that the data is not modified. (Use a write blocking device when possible)

Rule 5. The examination must be conducted in such a way as to prevent any modification of the evidence.

Rule 6. The chain of the custody of all evidence must be clearly maintained to provide an audit log of whom might have accessed the evidence and at what time.


All of the does not come without difficulties. There is an enhanced awareness amongst offenders of the nature of electronic evidence and the use of techniques to hide evidence. The skillful user makes the examiner’s job difficult, if not impossible. There is an increasing use of tools to hinder forensics - secure deletion tools, encryption tools, automated “scrubbing” tools, digital compression, steganography, remote storage, and audit disabling. Add to this the difficulty in placing a specific person at a specific computer without additional evidence, be it CCTV or Access Control Systems. Computer forensics is useful, but not always a silver bullet.

Not all incidents require of justify the full rigor of a forensic analysis. There are a number of factors affecting the decision to proceed, for instance, the seniority of staff. It is generally accepted that senior staff are more likely to appeal disciplinary procedures or otherwise respond. The background of staff is another important consideration. Staff with a legal, HR or union background may have other motivations. Obviously, if an investigation involves staff with a financial motive to appeal a disciplinary action, a forensic analysis that uncovers some compelling evidence may offer the organization a strong negotiation tool.