diff --git a/infra-monitoring/templates/exporter/blackbox/prometheus-rules.yaml b/infra-monitoring/templates/exporter/blackbox/prometheus-rules.yaml
index bf9d002..1a4117e 100644
--- a/infra-monitoring/templates/exporter/blackbox/prometheus-rules.yaml
+++ b/infra-monitoring/templates/exporter/blackbox/prometheus-rules.yaml
@@ -23,7 +23,7 @@ spec:
             `}}
 
         - alert: "BlackboxProbeFailed"
-          expr: 'probe_success{ {{ $filter }}, instancetype!="server" } == 0'
+          expr: 'sum(probe_success{ {{ $filter }}, instancetype!="server"}) without (job) / count(probe_success{ {{ $filter }}, instancetype!="server"}) without (job) < 0.5'
           for: "5m"
           labels:
             severity: "critical"
@@ -36,7 +36,7 @@ spec:
     - name: "ICMP"
       rules:
         - alert: "BlackboxProbeIcmpFailed"
-          expr: 'probe_success{ {{ $filter }}, instancetype="server" } == 0'
+          expr: 'sum(probe_success{ {{ $filter }}, instancetype="server"}) without (job) / count(probe_success{ {{ $filter }}, instancetype="server"}) without (job) < 0.5'
           for: "5m"
           labels:
             severity: "critical"