diff --git a/utils/README.md b/utils/README.md
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--- /dev/null
+++ b/utils/README.md
@@ -0,0 +1,12 @@
+Useful Tools
+===========
+
+autoban.py
+----------
+
+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
+attack. Default is 3.
diff --git a/utils/autoban.py b/utils/autoban.py
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+++ b/utils/autoban.py
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+#!/usr/bin/python
+# -*- coding: utf-8 -*-
+
+# Copyright (c) 2015 clowwindy
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in
+# all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+# SOFTWARE.
+
+from __future__ import absolute_import, division, print_function, \
+    with_statement
+
+import os
+import sys
+import argparse
+
+if __name__ == '__main__':
+    parser = argparse.ArgumentParser(description='See README')
+    parser.add_argument('-c', '--count', default=3, type=int,
+                        help='with how many failure times it should be '
+                             'considered an attack')
+    config = parser.parse_args()
+    ips = {}
+    banned = set()
+    for line in sys.stdin:
+        if 'can not parse header when' in line:
+            ip = line.split()[-1].split(':')[0]
+            if ip not in ips:
+                ips[ip] = 1
+                print(ip)
+            else:
+                ips[ip] += 1
+            if ip not in banned and ips[ip] >= config.count:
+                banned.add(ip)
+                cmd = 'iptables -A INPUT -s %s -j DROP' % ip
+                print(cmd, file=sys.stderr)
+                os.system(cmd)