Once a social engineer knows how things work inside the targeted company, it becomes easy to use that knowledge to develop rapport with legitimate employees. Companies need to prepare for social engineering attacks from current or former employees who may have an axe to grind. Background checks may be helpful to weed out prospects who may have a propensity toward this type of behavior. But in most cases, these people will be extremely difficult to detect. The only reasonable safeguard in these cases is to enforce and audit procedures for verifying identity, including the person's employment status, prior to disclosing any information to anyone not personally known to still be with the company.