A hacker with privileged access to a Windows 10 computer can configure it to act as a web proxy, which allows the attacker to target devices and services on the network through the compromised computer. The probes and attacks appear to originate from the Windows 10 computer, making it difficult to detect the attacker's actual location.
Network enumeration is one of the essential phases of an attack, but it can take a lot of time and effort depending on the size. We've all been spoiled by Nmap and similar tools, and while there is a learning curve involved, they are extremely useful. But there's also GoScan, a tool that builds upon Nmap, offering an automated way to enumerate networks and services quickly.
To name just a few companies, VK, µTorrent, and ClixSense all suffered significant data breaches at some point in the past. The leaked password databases from those and other online sites can be used to understand better how human-passwords are created and increase a hacker's success when performing brute-force attacks.
Leaving your wireless router at its default settings is a bad idea. The sad thing is, most people still do it. Once they've penetrated your network, hackers will change your router settings so they'll have an easy way back in. This allows them to change your network into a shell or proxy so they can forward their traffic anonymously through you when committing other dirty deeds.