add APT33 as identified by FireEye

clusters/threat-actor.json

@@ -663,6 +663,17 @@
       "value": "Charming Kitten",
       "description": "Charming Kitten (aka Parastoo, aka Newscaster) is an group with a suspected nexus to Iran that targets organizations involved in government, defense technology, military, and diplomacy sectors."
     },
+    {
+      "meta": {
+        "country": "IR",
+        "synonyms": [],
+        "refs": [
+          "https://www.fireeye.com/blog/threat-research/2017/09/apt33-insights-into-iranian-cyber-espionage.html"
+        ]
+      },
+      "description": "Our analysis reveals that APT33 is a capable group that has carried out cyber espionage operations since at least 2013. We assess APT33 works at the behest of the Iranian government.",
+      "value": "APT33"
+    },
     {
       "meta": {
         "country": "IR",