Add new subsection for signature packs.

README.md

@@ -45,6 +45,7 @@ Many cybersecurity professionals enable racist state violence, wittingly or unwi
   - [Service and performance monitoring](#service-and-performance-monitoring)
   - [Threat hunting](#threat-hunting)
 - [Threat intelligence](#threat-intelligence)
+  - [Threat signature packages and collections](#threat-signature-packages-and-collections)
 - [Tor Onion service defenses](#tor-onion-service-defenses)
 - [Transport-layer defenses](#transport-layer-defenses)
 - [macOS-based defenses](#macos-based-defenses)
@@ -307,6 +308,11 @@ See also [awesome-threat-intelligence](https://github.com/hslatman/awesome-threa
 - [Viper](https://github.com/viper-framework/viper) - Binary analysis and management framework enabling easy organization of malware and exploit samples.
 - [YARA](https://github.com/VirusTotal/yara) - Tool aimed at (but not limited to) helping malware researchers to identify and classify malware samples, described as "the pattern matching swiss army knife" for file patterns and signatures.
 
+### Threat signature packages and collections
+
+- [FireEye's Red Team Tool Countermeasures](https://github.com/fireeye/red_team_tool_countermeasures) - Collection of Snort and YARA rules to detect attacks carried out with FireEye's own Red Team tools, first released after FireEye disclosed a breach in December 2020.
+- [YARA Rules](https://github.com/Yara-Rules/rules) - Project covering the need for IT security researchers to have a single repository where different Yara signatures are compiled, classified and kept as up to date as possible.
+
 ## Tor Onion service defenses
 
 See also [awesome-tor](https://github.com/ajvb/awesome-tor).