diff --git a/lxc/execute b/lxc/execute
index 824b578..2f8a9c6 100755
--- a/lxc/execute
+++ b/lxc/execute
@@ -37,7 +37,12 @@ else
     echo $newinc > $dir/i
 fi
 exec 200>&-
-
+# Prevent users from spying on each other
+lxc-attach --clear-env -n piston -- \
+	/bin/bash -l -c "\
+		chown runner$newinc: -R /tmp/$epoch ;\
+		chmod 700 /tmp/$epoch ;\
+		" > /dev/null 2>&1
 # runner
 timeout -s KILL 20 \
     lxc-attach --clear-env -n piston -- \