APT and Malware Information Resources
Lots of information on different types of malware, threat actors, etc.
https://github.com/CyberMonitor/APT_CyberCriminal_Campagin_Collections
One of my favorite books on malware. The link is to the sample malware in the book.
https://idafchev.github.io/exploit/2017/09/26/writing_windows_shellcode.html
https://0x00sec.org/t/malware-writing-python-malware-part-1/11700