1 00:00:00,960 --> 00:00:08,280 Hello, everyone, and welcome to this video and this video we are going to understand about what is 2 00:00:08,280 --> 00:00:08,910 DNS. 3 00:00:10,050 --> 00:00:18,270 Why are we going to learn about DNS, DNS is a very, very important to understand how the communication 4 00:00:18,270 --> 00:00:25,450 is happening between the client and the server or how the client is actually able to reach to the server. 5 00:00:26,280 --> 00:00:30,870 There are many different records that are listed into a DNS. 6 00:00:32,090 --> 00:00:40,460 And for subdomain take-over types of attack, we need to understand actually how DNS works, because 7 00:00:40,460 --> 00:00:47,320 that will make this process much more simpler to understand subdomain tekoa when liabilities. 8 00:00:48,650 --> 00:00:51,020 So first, clearing the basics about DNS. 9 00:00:51,950 --> 00:00:55,660 DNS stands for domain name system or domain name service. 10 00:00:56,390 --> 00:01:05,010 It runs on port number 53 and DNS itself has multiple records, as you can see on the screen. 11 00:01:05,720 --> 00:01:10,610 So let's start with the first record, which is the A record, as you can see here. 12 00:01:11,300 --> 00:01:17,190 So A record means the hostname will point to an IP address. 13 00:01:17,780 --> 00:01:19,370 What does this mean actually? 14 00:01:20,090 --> 00:01:22,050 So into any server. 15 00:01:22,160 --> 00:01:28,280 So let's say the server is srsecure.xyz. 16 00:01:28,850 --> 00:01:34,830 So into this server there will be A record and that A record will tell. 17 00:01:35,180 --> 00:01:35,670 All right. 18 00:01:35,960 --> 00:01:43,640 So this hostname should be pointed to this specific IP address, for example, srsecure should 19 00:01:43,640 --> 00:01:51,050 be pointed to IP address, which is let's say 192.168.1.100. 20 00:01:51,740 --> 00:01:56,240 So now whenever a client like Rohit or you. 21 00:01:57,850 --> 00:02:04,480 Try to point srsecure.xyz into your browser, or when you try to open this into your 22 00:02:04,480 --> 00:02:11,800 URL bar of your Chrome browser or Firefox browser, you are automatically pointing to this IP address 23 00:02:11,800 --> 00:02:16,660 or you are able to open the website, which is hosted under this particular IP address. 24 00:02:17,290 --> 00:02:26,080 How this works, this is working because of the A record when we are sending a request to srsecure.xyz 25 00:02:26,080 --> 00:02:35,260 then from its DNS records, a record checks that this hostname actually points to this IP 26 00:02:35,260 --> 00:02:35,710 address. 27 00:02:36,010 --> 00:02:41,550 And remember, machine does not understand names, machine understand numbers. 28 00:02:41,890 --> 00:02:49,840 So each server has its own unique IP address and by default we are pointing to this IP address and hence 29 00:02:49,840 --> 00:02:53,100 we are able to connect it to this IP address. 30 00:02:53,440 --> 00:02:57,580 Now, for example, if you want to see this practical, let me open up a new window. 31 00:02:58,480 --> 00:03:07,360 And here, here, let me try to ping Google dot com and you can see I'm getting a reply from Google 32 00:03:07,360 --> 00:03:09,460 dot com 64 bytes reply. 33 00:03:09,790 --> 00:03:13,660 And here you can see IP address from where I'm getting a reply from. 34 00:03:14,240 --> 00:03:17,440 Now, if I try to open Google dot com. 35 00:03:17,920 --> 00:03:20,230 So let me try to open Google dot com. 36 00:03:22,040 --> 00:03:29,520 over here and you can see I'm able to open it now if I give the IP address over here and hit enter. 37 00:03:29,890 --> 00:03:32,670 And let's see if I'm able to open it and it gets opened. 38 00:03:33,320 --> 00:03:41,000 Now, this means that I can open Google dot com with the help of the URL or the name, as well as with 39 00:03:41,000 --> 00:03:42,680 the help of the IP address. 40 00:03:43,340 --> 00:03:52,160 This is basically happening because the name itself is pointing to Google dot com and this happens due 41 00:03:52,160 --> 00:03:53,390 to A record. 42 00:03:54,650 --> 00:03:55,190 All right. 43 00:03:55,520 --> 00:03:58,870 Let's move ahead to the next record, which is the CName record. 44 00:03:59,420 --> 00:04:05,770 Now, CName itself, the name is C, which stands for canonical. 45 00:04:06,350 --> 00:04:09,020 Now, this points hostname to hostname name. 46 00:04:09,590 --> 00:04:10,430 What does this mean? 47 00:04:10,880 --> 00:04:13,670 This means that, for example. 48 00:04:16,100 --> 00:04:18,530 srsecure.xyz. 49 00:04:19,040 --> 00:04:26,780 Now, if I write over here, let's say, www.srsecure.xyz this means if anyone 50 00:04:26,780 --> 00:04:35,240 types this into their browsers, then they should automatically get redirected to a srsecure.xyz 51 00:04:35,240 --> 00:04:38,360 and not get redirected to any other Web site. 52 00:04:38,930 --> 00:04:43,460 Now, here's what we have done, is we are pointing a hostname to a hostname. 53 00:04:44,000 --> 00:04:47,200 Now this relationship is called CName 54 00:04:47,660 --> 00:04:51,560 So let's see the practical quickly and understand how this actually works. 55 00:04:53,000 --> 00:04:58,550 So let me just quickly login into my C Panel server and let's quickly see this. 56 00:05:00,440 --> 00:05:06,290 So as you can see over here, I have logged in successfully into my server and here I am into my zone 57 00:05:06,290 --> 00:05:09,960 record, which is basically the DNS, as you can see over here. 58 00:05:10,490 --> 00:05:10,940 All right. 59 00:05:11,240 --> 00:05:15,110 Now, let me quickly show you A record, which is this button. 60 00:05:15,110 --> 00:05:19,270 You can see a hostname is pointing to an IP address. 61 00:05:19,610 --> 00:05:23,350 So this is the IP address of the server of srsecure.xyz. 62 00:05:23,900 --> 00:05:30,890 And if I show you if I try to remove this and if I tried to type a hostname, it's a Google dot com, 63 00:05:30,980 --> 00:05:37,610 then it will throw error and it would say you must specify a valid IP before address, which means I 64 00:05:37,610 --> 00:05:40,580 cannot point a hostname into a record. 65 00:05:40,820 --> 00:05:42,280 And we already learned that. 66 00:05:43,100 --> 00:05:44,700 So I'm just going to cancel this. 67 00:05:45,110 --> 00:05:45,590 All right. 68 00:05:45,980 --> 00:05:47,820 Now let's see a CName record. 69 00:05:48,080 --> 00:05:54,980 So for CName record as you can see over here a host name, which is www.srsecure.xyz 70 00:05:54,980 --> 00:06:00,320 is pointing to srsecure.xyz through a CName. 71 00:06:00,620 --> 00:06:06,150 And if I tried to modify this and let's say I put an IP address, then it is going to throw error, 72 00:06:06,150 --> 00:06:13,820 which says you must specify a valid CName record because this is not a canonical name, it is an IP 73 00:06:13,820 --> 00:06:19,700 address and we have seen in Cname record we point host names to host name. 74 00:06:20,300 --> 00:06:27,650 And if I try to write Google dot com over here, then anyone who visits the www.srsecure.xyz 75 00:06:27,650 --> 00:06:30,610 is going to get redirected to Google dot com. 76 00:06:31,220 --> 00:06:42,230 So let's do this simple experiment when I'm going to redirect www to srsecure.xyz to GitHub 77 00:06:42,230 --> 00:06:42,770 dot com. 78 00:06:43,130 --> 00:06:49,890 So I have just created this new CName right now and let's see if this works or not. 79 00:06:50,210 --> 00:06:51,920 So let me first copy this. 80 00:06:54,600 --> 00:07:01,920 let me open my terminal, and let's see if we are able to see if this is working or not. 81 00:07:02,370 --> 00:07:06,890 So let me just try to ping this first and you can see I'm getting a reply. 82 00:07:07,260 --> 00:07:07,710 All right. 83 00:07:07,980 --> 00:07:12,750 So I'm getting a reply from this IP address and let's see, which is this IP address from where I'm 84 00:07:12,750 --> 00:07:13,530 getting reply. 85 00:07:14,520 --> 00:07:20,780 And you can see I'm getting an IP address from I'm getting a ping reply from Amazon AWS. 86 00:07:21,240 --> 00:07:21,870 All right. 87 00:07:22,260 --> 00:07:23,760 Now, let's see. 88 00:07:24,150 --> 00:07:25,860 This IP address belongs to whom? 89 00:07:26,430 --> 00:07:31,310 So let me just try to open this into my browser and let's see what happens. 90 00:07:32,950 --> 00:07:41,470 And you can see I'm able to redirect to GitHub dot com, because this is where I actually pointed this 91 00:07:42,400 --> 00:07:45,300 CName record to github dot com. 92 00:07:45,700 --> 00:07:48,810 Therefore, I'm successfully getting redirected over here. 93 00:07:49,150 --> 00:07:52,480 And this is how actually CName record Works.