File /usr/libexec/squid/BLOCK_ALL will block all web access if it exist

files/squid/helpers/rules.d/opendsa.rules

 // OpenDSA
 
-// ^.* false
-
 ^https?://www\.ida\.liu\.se/edu/ugrad/datortenta/OpenDSA/Books/TDDD86_200317/.*  true
 
 ^https?://www\.ida\.liu\.se/edu/ugrad/datortenta/OpenDSA/Books/.*                false

files/squid/helpers/squid-url-rewrite.py

@@ -74,6 +74,10 @@ def main():
     
     ruleset = list()
 
+    block_all = basedir + "/../BLOCK_ALL"
+    if os.path.isfile(block_all):
+        ruleset.append( ["^.*", False] )
+
     devel_rules = basedir + "/../devel.rules"
     if 'devel' in hostname and os.path.isfile(devel_rules):
         load_rules(ruleset, devel_rules)