Spearfishing is probably the lowest risk and easiest way to get access to a specific network. The attacker can get a bunch of info about an organization (technologies used, people employed, physical locations) through LinkedIn or whatever social media website, and then target a specific person.

Once a target is identified, the next step would be getting that person to follow a link to type in a password, or getting them to install malware, or do whatever it is the attacker wants them to do. I read an article about a dude that got fairly big companies to pay him money by just sending fake bills.

The enemy of my enemy… also enemy.