Government resources

https://www.cisa.gov/uscert/ncas/alerts.xml

https://www.cisa.gov/uscert/ncas/current-activity.xml

https://www.cisa.gov/uscert/ncas/analysis-reports.xml

https://www.cisa.gov/uscert/ncas/bulletins.xml

Malware

https://www.virustotal.com/gui/home/upload

https://bazaar.abuse.ch/

https://mandiant.github.io/capa/explorer/#/

https://malpedia.caad.fkie.fraunhofer.de/

REversing

https://dogbolt.org/

https://godbolt.org/

https://github.com/dnSpy/dnSpy

Malware Analysis

https://cloud.binary.ninja/

https://github.com/ReFirmLabs/binwalk