diff --git a/src/fgai/profile_suggestions.py b/src/fgai/profile_suggestions.py
index 5dd660a..1566631 100644
--- a/src/fgai/profile_suggestions.py
+++ b/src/fgai/profile_suggestions.py
@@ -164,6 +164,7 @@ IGNORED_DISCOVERY_FIELDS = {
     "fgai_stream_id",
     "fgai_stream_name",
 }
+EMPTY_DISCOVERY_VALUES = {"", "-", "--", "unknown", "n/a", "none", "null", "nil", "undefined", "[]", "{}"}
 
 
 def _stream_id(event: LogEvent) -> str:
@@ -182,6 +183,11 @@ def _is_number(value: str) -> bool:
         return False
 
 
+def _has_discovery_value(value: object) -> bool:
+    text = str(value).strip()
+    return text.lower() not in EMPTY_DISCOVERY_VALUES
+
+
 def _pick_present(priority: tuple[str, ...], coverage: Counter[str], total: int, *, min_ratio: float = 0.05, limit: int = 6) -> list[str]:
     selected = []
     for field in priority:
@@ -436,7 +442,7 @@ def suggest_stream_profiles(events: list[LogEvent], *, existing_profiles: dict[s
         detector_counts: Counter[str] = Counter()
         for event in stream_events:
             for field, value in event.fields.items():
-                if not value:
+                if not _has_discovery_value(value):
                     continue
                 coverage[field] += 1
                 if len(unique_values[field]) < 200:
diff --git a/tests/test_profile_suggestions.py b/tests/test_profile_suggestions.py
index e44caa1..017f8f7 100644
--- a/tests/test_profile_suggestions.py
+++ b/tests/test_profile_suggestions.py
@@ -22,6 +22,26 @@ class ProfileSuggestionTests(unittest.TestCase):
         self.assertIn("hitcount", profile["numeric_fields"])
         self.assertIn("deny_action", profile["detectors"])
 
+    def test_placeholder_winlog_fields_do_not_make_firewall_windows(self):
+        events = [
+            parse_log_line(
+                f"fgai_stream_id=firewall fgai_stream='Firewall Logs' srcip=10.0.0.{index} dstip=8.8.8.8 "
+                f"dstport=443 action=deny policyid=12 eventid=- winlog.channel=- winlog.event_id=- "
+                f"winlog.event_data.targetusername=- hostname=- username=- timestamp=2026-06-29T10:00:{index:02d}Z"
+            )
+            for index in range(1, 25)
+        ]
+
+        suggestion = suggest_stream_profiles(events)[0]
+        profile = suggestion["profile"]
+
+        self.assertEqual(suggestion["detected_log_type"], "firewall")
+        self.assertNotIn("username", profile["entity_fields"])
+        self.assertNotIn("hostname", profile["entity_fields"])
+        self.assertIn("srcip", profile["entity_fields"])
+        self.assertIn("policyid", profile["categorical_fields"])
+        self.assertIn("deny_action", profile["detectors"])
+
     def test_suggests_windows_event_fields(self):
         events = [
             parse_log_line(