diff --git a/backend/app.py b/backend/app.py
index c60a6fa..c4bcad0 100644
--- a/backend/app.py
+++ b/backend/app.py
@@ -1,3 +1,4 @@
+from base64 import b64decode
 import sqlite3, subprocess, sys, threading, bcrypt, secrets, time, re
 from flask import Flask, jsonify, request, abort, session
 from functools import wraps
@@ -262,7 +263,6 @@ def get_regex_delete(regex_id):
     
     return {'status': 'ok'}
 
-
 @app.route('/api/regexes/add', methods = ['POST'])
 @login_required
 def post_regexes_add():
@@ -283,9 +283,17 @@ def post_regexes_add():
             return abort(400)
     except Exception:
         return abort(400)
-    db.query("INSERT INTO regexes (service_id, regex, is_blacklist, mode) VALUES (?, ?, ?, ?);", 
+
+    try:
+        re.compile(b64decode(req["regex"]))
+    except Exception:
+        return {"status":"Invalid regex"}
+    try:
+        db.query("INSERT INTO regexes (service_id, regex, is_blacklist, mode) VALUES (?, ?, ?, ?);", 
                 (req['service_id'], req['regex'], req['is_blacklist'], req['mode']))
-    
+    except sqlite3.IntegrityError:
+        return {'status': 'An identical regex already exists'}
+
     firewall.fire_update(req['service_id'])
     return {'status': 'ok'}
 
@@ -345,6 +353,7 @@ if __name__ == '__main__':
             'value': 'VARCHAR(100) NOT NULL',
         },
     })
+    db.query("CREATE UNIQUE INDEX IF NOT EXISTS unique_regex_service ON regexes (regex,service_id,is_blacklist,mode);")
 
     if DEBUG:
         app.run(host="0.0.0.0", port=8080 ,debug=True)
diff --git a/backend/utils.py b/backend/utils.py
index 955b0dd..ef60ffa 100755
--- a/backend/utils.py
+++ b/backend/utils.py
@@ -1,6 +1,6 @@
 from asyncore import file_dispatcher
 from proxy import Filter, Proxy
-import random, string, os, threading, sqlite3, time
+import random, string, os, threading, sqlite3, time, atexit
 from kthread import KThread
 from base64 import b64decode
 
@@ -68,12 +68,13 @@ class STATUS:
     STOP = "stop"
     PAUSE = "pause"
     ACTIVE = "active"
-
+ 
 class ProxyManager:
     def __init__(self, db:SQLite):
         self.db = db
         self.proxy_table = {}
         self.lock = threading.Lock()
+        atexit.register(self.clear)
 
     def __clear_proxy_table(self):
         with self.lock:
@@ -81,6 +82,13 @@ class ProxyManager:
                 if not self.proxy_table[key]["thread"].is_alive():
                     del self.proxy_table[key]
 
+    def clear(self):
+        with self.lock:
+            for key in list(self.proxy_table.keys()):
+                if self.proxy_table[key]["thread"].is_alive():
+                    self.proxy_table[key]["thread"].kill()
+                del self.proxy_table[key]
+
     def reload(self):
         self.__clear_proxy_table()
         with self.lock: 
diff --git a/frontend/src/components/AddNewRegex.tsx b/frontend/src/components/AddNewRegex.tsx
index 142894e..a440eb9 100755
--- a/frontend/src/components/AddNewRegex.tsx
+++ b/frontend/src/components/AddNewRegex.tsx
@@ -2,7 +2,7 @@ import { Button, Group, Space, TextInput, Notification, Switch, NativeSelect, To
 import { useForm } from '@mantine/hooks';
 import React, { useState } from 'react';
 import { RegexAddForm } from '../js/models';
-import { addregex, b64encode, getHumanReadableRegex, okNotify, validateRegex } from '../js/utils';
+import { addregex, b64encode, getHumanReadableRegex, okNotify } from '../js/utils';
 import { ImCross } from "react-icons/im"
 import FilterTypeSelector from './FilterTypeSelector';
 
@@ -26,7 +26,7 @@ function AddNewRegex({ opened, onClose, service }:{ opened:boolean, onClose:()=>
             percentage_encoding:false
         },
         validationRules:{
-            regex: (value) => value !== "" && validateRegex(value),
+            regex: (value) => value !== "",
             type: (value) => ["blacklist","whitelist"].includes(value),
             mode: (value) => ['C -> S', 'S -> C', 'C <-> S'].includes(value)
         }
@@ -35,6 +35,7 @@ function AddNewRegex({ opened, onClose, service }:{ opened:boolean, onClose:()=>
     const close = () =>{
         onClose()
         form.reset()
+        setError(null)
     }
 
     const [submitLoading, setSubmitLoading] = useState(false)
@@ -64,9 +65,12 @@ function AddNewRegex({ opened, onClose, service }:{ opened:boolean, onClose:()=>
                 setSubmitLoading(false)
                 close();
                 okNotify(`Regex ${getHumanReadableRegex(request.regex)} has been added`, `Successfully added ${request.is_blacklist?"blacklist":"whitelist"} regex to ${request.service_id} service`)
+            }else if (res.toLowerCase() === "invalid regex"){
+                setSubmitLoading(false)
+                form.setFieldError("regex", "Invalid Regex")
             }else{
                 setSubmitLoading(false)
-                setError("Invalid request! [ "+res+" ]")
+                setError("Error: [ "+res+" ]")
             }
         }).catch( err => {
             setSubmitLoading(false)
@@ -84,7 +88,7 @@ function AddNewRegex({ opened, onClose, service }:{ opened:boolean, onClose:()=>
                 {...form.getInputProps('regex')}
             />
             <Space h="md" />
-            <Tooltip label="To represent binary data use URL encoding. Example: %01" transition="slide-left" openDelay={600} transitionDuration={250} transitionTimingFunction="ease"  
+            <Tooltip label="To represent binary data use URL encoding. Example: %01" transition="slide-left" openDelay={1500} transitionDuration={250} transitionTimingFunction="ease"  
                     color="gray" wrapLines width={220} withArrow position='right'>      
                 <Switch
                     label="Use percentage encoding for binary values"
diff --git a/frontend/src/components/AddNewService.tsx b/frontend/src/components/AddNewService.tsx
index 2331532..a59238f 100755
--- a/frontend/src/components/AddNewService.tsx
+++ b/frontend/src/components/AddNewService.tsx
@@ -21,6 +21,7 @@ function AddNewService({ opened, onClose }:{ opened:boolean, onClose:()=>void })
     const close = () =>{
         onClose()
         form.reset()
+        setError(null)
     }
 
     const [submitLoading, setSubmitLoading] = useState(false)
diff --git a/frontend/src/js/utils.tsx b/frontend/src/js/utils.tsx
index 3efd86c..e58361e 100755
--- a/frontend/src/js/utils.tsx
+++ b/frontend/src/js/utils.tsx
@@ -159,17 +159,6 @@ export function okNotify(title:string, description:string ){
     });
 }
 
-export function validateRegex(pattern:string) {
-    return true; // TO TEST
-    try {
-        new RegExp(pattern);
-        return true;
-    }
-    catch(e) {
-        return false;
-    }
-}
-
 export function b64encode(data:string){
     return Buffer.from(data).toString('base64')
 }