diff --git a/rules/REQUEST-913-SCANNER-DETECTION.conf b/rules/REQUEST-913-SCANNER-DETECTION.conf
index 2b21cef..335dad2 100644
--- a/rules/REQUEST-913-SCANNER-DETECTION.conf
+++ b/rules/REQUEST-913-SCANNER-DETECTION.conf
@@ -31,6 +31,7 @@ SecRule TX:EXECUTING_PARANOIA_LEVEL "@lt 1" "id:913012,phase:2,pass,nolog,skipAf
 # 913101 - scripting/generic HTTP clients (data file scripting-user-agents.data)
 # 913102 - web crawlers/bots (data file crawlers-user-agents.data)
 #
+# Chained rule is doing whitelist for YUM package manager of CentOS / Fedore.
 SecRule REQUEST_HEADERS:User-Agent "@pmFromFile scanners-user-agents.data" \
     "id:913100,\
     phase:2,\
@@ -49,10 +50,12 @@ SecRule REQUEST_HEADERS:User-Agent "@pmFromFile scanners-user-agents.data" \
     tag:'PCI/6.5.10',\
     ver:'OWASP_CRS/3.3.4',\
     severity:'CRITICAL',\
-    setvar:'tx.anomaly_score_pl1=+%{tx.critical_anomaly_score}',\
-    setvar:'ip.reput_block_flag=1',\
-    setvar:'ip.reput_block_reason=%{rule.msg}',\
-    expirevar:'ip.reput_block_flag=%{tx.reput_block_duration}'"
+    chain"
+    SecRule MATCHED_VARS "!@rx ^urlgrabber/[0-9\.]+ yum/[0-9\.]+$" \
+        "setvar:'tx.anomaly_score_pl1=+%{tx.critical_anomaly_score}',\
+        setvar:'ip.reput_block_flag=1',\
+        setvar:'ip.reput_block_reason=%{rule.msg}',\
+        expirevar:'ip.reput_block_flag=%{tx.reput_block_duration}'"
 
 SecRule REQUEST_HEADERS_NAMES|REQUEST_HEADERS "@pmFromFile scanners-headers.data" \
     "id:913110,\