Over the last number of years there has been a noticeable rise in the number of reported targeted attacks, which are also commonly referred to as advanced persistent threats (APTs). Notable examples of said attacks include the Red October campaign or the IXESHE APT.
What sets a targeted attack apart from a widespread attack is purely the motivation behind the attackers and their victims. The actual tools used are largely irrelevant; the tools are identical, but the motivations of the attackers and the targeted victims set a targeted attack apart. For example, a Remote Access Tool (RAT) that infects users across 50 countries would be considered a widespread attack – while the same attack against two nuclear power plants against no one else is an example of a targeted attack. The tool is identical but the motivation of the attackers and their chosen targets set the attacks apart.
One thing that clear about targeted attacks is that they are difficult to detect, and not much research has been conducted so far in detecting these attacks.