diff --git a/modules/nat_detector/__init__.py b/modules/nat_detector/__init__.py
new file mode 100644
index 000000000..a0162f7b2
--- /dev/null
+++ b/modules/nat_detector/__init__.py
@@ -0,0 +1,2 @@
+# This file is part of Viper - https://github.com/botherder/viper
+# See the file 'LICENSE' for copying permission.
diff --git a/modules/nat_detector/nat_detector.py b/modules/nat_detector/nat_detector.py
new file mode 100644
index 000000000..173a9a2fa
--- /dev/null
+++ b/modules/nat_detector/nat_detector.py
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+# Ths is a template module for you to copy and create your own slips module
+# Instructions
+# 1. Create a new folder on ./modules with the name of your template. Example:
+#    mkdir modules/anomaly_detector
+# 2. Copy this template file in that folder.
+#    cp modules/template/template.py modules/anomaly_detector/anomaly_detector.py
+# 3. Make it a module
+#    touch modules/template/__init__.py
+# 4. Change the name of the module, description and author in the variables
+# 5. The file name of the python module (template.py) MUST be the same as the name of the folder (template)
+# 6. The variable 'name' MUST have the public name of this module. This is used to ignore the module
+# 7. The name of the class MUST be 'Module', do not change it.
+
+# Must imports
+from slips_files.common.abstracts import Module
+import multiprocessing
+from slips_files.core.database.database import __database__
+from slips_files.common.config_parser import ConfigParser
+from slips_files.common.slips_utils import utils
+import sys
+import traceback
+
+# Your imports
+import json
+import queue
+import datetime
+
+class FlowList:
+    def __init__(self, buffer_size = 300, threshold = 4.0):
+        self.flows = {} #saddr: queue of buffer_size most recent flows
+        self.buffer_size = buffer_size
+        self.stats_list = [
+            'dur', 'pkts', 'allbytes'
+        ]
+        self.stats = {} #saddr: dict of running sum of each stat in stats_list
+        self.baselines = dict.fromkeys(self.stats_list, 0) #stat: per flow avg across all sources
+        self.threshold = threshold
+        self.nat_ips = set()
+        self.most_recent_nat = None #data value gets consumed after reading once
+    def add_flow(self, flow_data):
+        saddr = flow_data['saddr']
+        src_before = len(self.flows)
+        if saddr not in self.flows:
+            self.flows[saddr] = queue.Queue()
+            self.stats[saddr] = dict.fromkeys(self.stats_list, 0)
+        flowq = self.flows[saddr]
+        while not flowq.empty() and self.flows[saddr].qsize() >= self.buffer_size:
+            popped_flow = self.get_stats_list(flowq.get())
+            self.update_stats(saddr,self.get_stats_list(popped_flow), multiplier=-1)
+        flowq.put(flow_data)
+        # each flow->update saddr average, update global average, check if current src passes threshold
+        stat_deltas = self.get_stats_list(flow_data)
+        stat_avg = self.get_stat_avg(saddr)
+        self.update_stats(saddr, stat_deltas)
+        for stat in self.stats_list:
+            self.baselines[stat] = self.baselines[stat]*src_before + stat_avg[stat]
+            self.baselines[stat] /= len(self.flows)
+        if self.stats_above_threshold(stat_avg):
+            self.nat_ips.add(saddr)
+            self.most_recent_nat = saddr
+    def update_stats(self, saddr, stats_dict, multiplier=1):
+        for stat in self.stats_list:
+            self.stats[saddr][stat] += multiplier*stats_dict[stat]
+    def get_stats_list(self, flow_data):
+        return {
+            'dur': float(flow_data['dur']),
+            'pkts': flow_data['pkts'],
+            'allbytes': flow_data['allbytes']
+        }
+    def get_stat_avg(self, saddr):
+        avg = {}
+        stats = self.stats[saddr]
+        num = self.flows[saddr].qsize()
+        for key in self.stats_list:
+            avg[key] = stats[key]/num
+        return avg
+    def stats_above_threshold(self, stats):
+        for key in self.stats_list:
+            if key not in stats:
+                raise Exception('stats_exceed_threshold: parameter doesn\'t contain required keys')
+            if stats[key] > self.baselines[key]*self.threshold:
+                return True
+        return False
+    def garbage_collect_nat_ips(self):
+        for saddr in self.nat_ips:
+            stat_avg = self.get_stat_avg(saddr)
+            if self.stats_above_threshold(stat_avg):
+                self.nat_ips.add(saddr)
+            else:
+                self.nat_ips.discard(saddr)
+    def get_nat_ips(self):
+        return self.nat_ips
+    def get_most_recent_nat(self):
+        most_recent = self.most_recent_nat
+        self.most_recent_nat = None
+        return most_recent
+class Module(Module, multiprocessing.Process):
+    # Name: short name of the module. Do not use spaces
+    name = 'NAT Detector'
+    description = 'Detect IPs running NAT'
+    authors = ['Daniel Yang']
+
+    def __init__(self, outputqueue, redis_port):
+        multiprocessing.Process.__init__(self)
+        # All the printing output should be sent to the outputqueue.
+        # The outputqueue is connected to another process called OutputProcess
+        self.outputqueue = outputqueue
+        __database__.start(redis_port)
+        # To which channels do you wnat to subscribe? When a message
+        # arrives on the channel the module will wakeup
+        # The options change, so the last list is on the
+        # slips/core/database.py file. However common options are:
+        # - new_ip
+        # - tw_modified
+        # - evidence_added
+        # Remember to subscribe to this channel in database.py
+        self.c1 = __database__.subscribe('new_flow')
+
+    def print(self, text, verbose=1, debug=0):
+        """
+        Function to use to print text using the outputqueue of slips.
+        Slips then decides how, when and where to print this text by taking all the processes into account
+        :param verbose:
+            0 - don't print
+            1 - basic operation/proof of work
+            2 - log I/O operations and filenames
+            3 - log database/profile/timewindow changes
+        :param debug:
+            0 - don't print
+            1 - print exceptions
+            2 - unsupported and unhandled types (cases that may cause errors)
+            3 - red warnings that needs examination - developer warnings
+        :param text: text to print. Can include format like 'Test {}'.format('here')
+        """
+
+        levels = f'{verbose}{debug}'
+        self.outputqueue.put(f'{levels}|{self.name}|{text}')
+
+    def shutdown_gracefully(self):
+        # Confirm that the module is done processing
+        __database__.publish('finished_modules', self.name)
+
+    def run(self):
+        utils.drop_root_privs()
+        # Main loop function
+        flow_list = FlowList()
+        last_garbage_collection = 0
+        while True:
+            try:
+                message = __database__.get_message(self.c1)
+                # Check that the message is for you. Probably unnecessary...
+                if message and message['data'] == 'stop_process':
+                    self.shutdown_gracefully()
+                    return True
+
+                if message and message['channel'] == 'new_flow':
+                    try:
+                        json_data = json.loads(json.loads(message['data'])['flow'])
+                        key = list(json_data.keys())[0]
+                        data = json.loads(json_data[key])
+                        if data['ts'] - last_garbage_collection > 120:
+                            flow_list.garbage_collect_nat_ips()
+                            last_garbage_collection = data['ts']
+                        flow_list.add_flow(data)
+                        most_recent = flow_list.get_most_recent_nat()
+                        #if detects NAT then displays most_recent
+                        #could also periodically correct nat_ips
+                        if most_recent:
+                            confidence = 0.8
+                            # how dangerous is this evidence? info, low, medium, high, critical?
+                            threat_level = 'high'
+
+                            # the name of your evidence, you can put any descriptive string here
+                            evidence_type = 'ConnectionToLocalDevice'
+                            # what is this evidence category according to IDEA categories 
+                            category = 'Anomaly.Connection'
+                            # which ip is the attacker here? the src or the dst?
+                            attacker_direction = 'srcip'
+                            # what is the ip of the attacker?
+                            attacker = data['saddr']
+                            # describe the evidence
+                            description = f'Detected an instance of NAT {data["saddr"]}'
+                            timestamp = datetime.datetime.fromtimestamp(data['ts']).strftime('%Y/%m/%d-%H:%M:%S')
+                            # the crrent profile is the source ip, this comes in 
+                            # the msg received in the channel
+                            msg_data = json.loads(message['data'])
+                            profileid = msg_data['profileid']
+                            # Profiles are split into timewindows, each timewindow is 1h, 
+                            # this comes in the msg received in the channel
+                            twid = msg_data['twid']
+
+                            __database__.setEvidence(evidence_type, attacker_direction, attacker, threat_level, confidence, description,
+                                                    timestamp, category, profileid=profileid, twid=twid)
+                    except Exception as e:
+                        data = "parse failed"
+                        self.print(e)
+                    # self.print(data, 1, 0)
+
+            except KeyboardInterrupt:
+                self.shutdown_gracefully()
+                return True
+            except Exception as inst:
+                exception_line = sys.exc_info()[2].tb_lineno
+                self.print(f'Problem on the run() line {exception_line}', 0, 1)
+                self.print(traceback.format_exc(), 0, 1)
+                return True