The “Web Proxy Event Analysis Cheat Sheet” can help SOCs and security analysts classify proxy events (blocks, alerts) and is based on my ideas and many ideas from experts that helped me collect detection ideas for this document.
You can download version 1.0 here.
We also recommend checking Sigma’s “proxy” section for detection rules that can be used to detect threats in web proxy or similar logs as long as they contain web connection information (EDR, HIDS etc.).