The UBS PaineWebber Case is an example of what can happen when an employee

The UBS PaineWebber Case is an example of what can happen when an employee (or someone who has inside access) decides to harm a business. Too many news stories contain similar situation, so we should be aware of the potential and prepare to prevent or mitigate adverse effects. 

After rereading this case what might have been some red flags indicating that Duronio was a disgruntled employee? Would any of those red flags also indicate that he would sabotage the network for revenge? How could this disaster have been prevented? What policies, procedures, or technology could have prevented such an attack by an employee with full network access?