update readme

utils/README.md

@@ -8,5 +8,11 @@ Automatically ban IPs that try to brute force crack the server.
 
     python autoban.py < /var/log/shadowsocks.log
 
-Use `-c` to specify with how many failure times it should be considered an
+Use `-c` to specify with how many failure times it should be considered as an
 attack. Default is 3.
+
+To continue watching for the log file:
+
+    nohup tail -f /var/log/shadowsocks.log | python autoban.py >log 2>log &
+
+Use with caution. Avoid to ban yourself.