1 1 00:00:00,870 --> 00:00:02,300 Now, before we start talking 2 2 00:00:02,300 --> 00:00:04,310 about network hacking, 3 3 00:00:04,310 --> 00:00:07,240 you need to have a basic understanding 4 4 00:00:07,240 --> 00:00:09,033 on how networks work. 5 5 00:00:10,150 --> 00:00:13,440 Now, we all know that a network usually contains 6 6 00:00:13,440 --> 00:00:17,290 a number of clients connected to each other, 7 7 00:00:17,290 --> 00:00:20,250 and clients usually connect to a network 8 8 00:00:20,250 --> 00:00:24,223 in order to share data or share a resource. 9 9 00:00:25,390 --> 00:00:27,570 A really good example of a resource 10 10 00:00:27,570 --> 00:00:30,400 that we all have connected to networks 11 11 00:00:30,400 --> 00:00:33,263 in order to access is the internet. 12 12 00:00:34,100 --> 00:00:37,640 So, we connect to Wi-Fi networks and even wired networks 13 13 00:00:37,640 --> 00:00:40,603 all the time just to access the internet. 14 14 00:00:41,800 --> 00:00:45,460 Now, all networks, whether it's Wi-Fi or wired, 15 15 00:00:45,460 --> 00:00:48,130 work on the same principle. 16 16 00:00:48,130 --> 00:00:52,890 They have a device that is considered as server. 17 17 00:00:52,890 --> 00:00:56,200 Now, in many cases, for example, in your home network, 18 18 00:00:56,200 --> 00:00:58,773 this server is your router. 19 19 00:00:59,700 --> 00:01:02,823 This is also referred to as an access point. 20 20 00:01:04,030 --> 00:01:08,380 Now, this router or server or access point 21 21 00:01:08,380 --> 00:01:13,380 is the only device that has access to the resource. 22 22 00:01:14,660 --> 00:01:18,130 So, none of these clients have direct access 23 23 00:01:18,130 --> 00:01:21,863 to the resource, even after connecting to the network. 24 24 00:01:22,910 --> 00:01:25,680 The only way they can access the resource 25 25 00:01:25,680 --> 00:01:28,223 is through the access point. 26 26 00:01:29,270 --> 00:01:32,690 So, let's say, for example, you're client number one 27 27 00:01:32,690 --> 00:01:34,970 and you connected to your home network 28 28 00:01:34,970 --> 00:01:39,220 over Wi-Fi or over ethernet, over a cable 29 29 00:01:39,220 --> 00:01:44,220 and then you opened your browser and you typed google.com. 30 30 00:01:44,370 --> 00:01:48,910 What happens is your computer will send the request 31 31 00:01:48,910 --> 00:01:53,250 to the access point asking for google.com. 32 32 00:01:53,250 --> 00:01:56,090 The access point has access to the resource, 33 33 00:01:56,090 --> 00:01:58,540 which is the internet in this example, 34 34 00:01:58,540 --> 00:02:01,823 so it's gonna go and look for google.com. 35 35 00:02:03,370 --> 00:02:05,910 It will receive google.com, 36 36 00:02:05,910 --> 00:02:09,780 and it'll forward that response to your computer, 37 37 00:02:09,780 --> 00:02:12,370 and as a result you will see the website 38 38 00:02:12,370 --> 00:02:14,483 loading on your browser. 39 39 00:02:15,610 --> 00:02:18,980 So if you actually go to your router at home 40 40 00:02:18,980 --> 00:02:21,450 and look at it, you'll see at the back 41 41 00:02:21,450 --> 00:02:24,350 it's connected through a cable to the wall 42 42 00:02:24,350 --> 00:02:27,723 and this is how it's getting its internet access. 43 43 00:02:28,600 --> 00:02:33,040 Therefore, it is the only device in your network 44 44 00:02:33,040 --> 00:02:36,030 that has direct access to the resource 45 45 00:02:36,030 --> 00:02:37,730 and none of your computers, 46 46 00:02:37,730 --> 00:02:40,500 none of the computers connected to the network 47 47 00:02:40,500 --> 00:02:44,130 can access the resource or can access the internet 48 48 00:02:44,130 --> 00:02:47,480 without the router, without the access point. 49 49 00:02:47,480 --> 00:02:50,560 So the only way for all of the connected clients 50 50 00:02:50,560 --> 00:02:54,503 to access the resource is to go through the router. 51 51 00:02:55,660 --> 00:02:59,060 Now, the data is transferred between clients 52 52 00:02:59,060 --> 00:03:02,380 and the access point as packets. 53 53 00:03:02,380 --> 00:03:04,900 So you can think of all of these arrows 54 54 00:03:04,900 --> 00:03:08,160 as a series of packets being transmitted 55 55 00:03:08,160 --> 00:03:13,160 between the client and the router as requests and responses. 56 56 00:03:14,670 --> 00:03:16,380 Now, in Wi-Fi networks, 57 57 00:03:16,380 --> 00:03:20,270 these packets are transmitted in the air. 58 58 00:03:20,270 --> 00:03:23,030 Therefore, if you have a wireless card 59 59 00:03:23,030 --> 00:03:26,260 and you're within range, you'll be able to capture 60 60 00:03:26,260 --> 00:03:29,083 all of these requests and responses. 61 61 00:03:30,000 --> 00:03:32,810 So, basically, you'll be able to see 62 62 00:03:32,810 --> 00:03:35,500 anything that any computer 63 63 00:03:35,500 --> 00:03:38,340 connected to the same network as you, 64 64 00:03:38,340 --> 00:03:40,880 thus on the internet, 65 65 00:03:40,880 --> 00:03:43,800 because they will have to send all of these data 66 66 00:03:43,800 --> 00:03:45,100 to the access point, 67 67 00:03:45,100 --> 00:03:48,030 and because they're sending this data in the air 68 68 00:03:48,030 --> 00:03:50,520 because you're in a WiFi network, 69 69 00:03:50,520 --> 00:03:52,470 you'll basically be able to capture 70 70 00:03:52,470 --> 00:03:54,550 these requests and responses. 71 71 00:03:54,550 --> 00:03:58,110 And you'll be able to see the URLs they visit, 72 72 00:03:58,110 --> 00:04:02,350 the usernames, the passwords they enter, the chat messages. 73 73 00:04:02,350 --> 00:04:06,670 Anything they do on the internet will be sent as packets 74 74 00:04:06,670 --> 00:04:10,433 and therefore you'll be able to capture it and analyze it. 75 75 00:04:11,300 --> 00:04:13,180 We'll talk more about that 76 76 00:04:13,180 --> 00:04:15,520 and more about how networks work 77 77 00:04:15,520 --> 00:04:17,560 as we go through the course 78 78 00:04:17,560 --> 00:04:19,940 but this is enough to get you going 79 79 00:04:19,940 --> 00:04:24,050 through the next few lectures, so that you can sniff data, 80 80 00:04:24,050 --> 00:04:26,060 analyze it and start launching 81 81 00:04:26,060 --> 00:04:28,553 some cool pre-connection attacks.