The most common source of attack against companies comes from:

Insiders, including current or former employees, contractors, or business partners, often possess authorized access to internal systems, data, and physical locations. This existing access gives them a significant advantage, making them a common source of malicious activity or unintentional security breaches, as they can bypass many external perimeter defenses.

Hackers, while a threat, typically refer to external actors who must breach external defenses first, unlike insiders who already have access.

Crackers are a specific type of malicious hacker, usually focused on breaking into systems or software, and are generally external threats.

Script kiddies are less sophisticated external attackers using pre-made tools, making them less likely to be the 'most common source' for targeted company attacks compared to insiders.

Spies are typically external actors, often state-sponsored, who aim to steal secrets, but are not necessarily the most common source of all attacks against companies.