1 1 00:00:00,280 --> 00:00:02,210 General network attacks. 2 2 00:00:02,210 --> 00:00:03,870 In this lesson, we're going to discuss 3 3 00:00:03,870 --> 00:00:06,510 some general network attacks that you may come across 4 4 00:00:06,510 --> 00:00:08,020 while working in the field. 5 5 00:00:08,020 --> 00:00:09,970 These attacks include things like on-path 6 6 00:00:09,970 --> 00:00:11,400 or Man in the Middle attacks, 7 7 00:00:11,400 --> 00:00:15,630 session hijacking, DNS poisoning and rogue DHCP servers. 8 8 00:00:15,630 --> 00:00:17,960 Let's jump right into our first type of attack, 9 9 00:00:17,960 --> 00:00:19,750 known as an on-path attack, 10 10 00:00:19,750 --> 00:00:22,130 but you may be more familiar with it by another name, 11 11 00:00:22,130 --> 00:00:24,930 the MITM or Man in the Middle attack. 12 12 00:00:24,930 --> 00:00:27,490 Now, a Man in the Middle attack occurs when an attacker 13 13 00:00:27,490 --> 00:00:29,280 puts themselves between the victim 14 14 00:00:29,280 --> 00:00:30,990 and the intended destination. 15 15 00:00:30,990 --> 00:00:33,790 For example, if you're trying to connect to yourbank.com 16 16 00:00:33,790 --> 00:00:34,623 from your laptop, 17 17 00:00:34,623 --> 00:00:36,640 and someone's able to get in between your laptop 18 18 00:00:36,640 --> 00:00:37,840 and the bank servers, 19 19 00:00:37,840 --> 00:00:40,100 this would be an on-path attack. 20 20 00:00:40,100 --> 00:00:41,270 In this type of attack, 21 21 00:00:41,270 --> 00:00:42,820 the attacker is simply going to have the ability 22 22 00:00:42,820 --> 00:00:44,530 to monitor whenever you're sending, 23 23 00:00:44,530 --> 00:00:46,420 or they can even manipulate it 24 24 00:00:46,420 --> 00:00:48,360 because they're in the middle of the communications 25 25 00:00:48,360 --> 00:00:50,100 between you and the server. 26 26 00:00:50,100 --> 00:00:52,120 For example, let's pretend I have a client 27 27 00:00:52,120 --> 00:00:54,570 who is client number 12345, 28 28 00:00:54,570 --> 00:00:57,630 and they want to conduct a transaction at their online bank. 29 29 00:00:57,630 --> 00:01:00,320 They go and they log on and they go to transfer $50 30 30 00:01:00,320 --> 00:01:01,480 to their account. 31 31 00:01:01,480 --> 00:01:05,940 Now they send a request to move $50 to account 12345 32 32 00:01:05,940 --> 00:01:07,070 from their checking account 33 33 00:01:07,070 --> 00:01:08,190 and they think that request 34 34 00:01:08,190 --> 00:01:10,320 went straight to the bank servers for processing, 35 35 00:01:10,320 --> 00:01:12,970 but little did they know they were in the middle 36 36 00:01:12,970 --> 00:01:15,780 of a Man in the Middle attack or on-path attack. 37 37 00:01:15,780 --> 00:01:17,420 So what happens? 38 38 00:01:17,420 --> 00:01:19,520 Well from this position of the Man in the Middle 39 39 00:01:19,520 --> 00:01:20,650 of the communication, 40 40 00:01:20,650 --> 00:01:22,720 they're sitting between the client and the bank. 41 41 00:01:22,720 --> 00:01:25,970 So the attacker can then change the amount from $50 42 42 00:01:25,970 --> 00:01:29,130 to $5,000, or they could change the bank account 43 43 00:01:29,130 --> 00:01:30,970 that funds are going to be transferred to. 44 44 00:01:30,970 --> 00:01:33,490 So instead of going to account 12345, 45 45 00:01:33,490 --> 00:01:36,820 it now goes to 67890 instead. 46 46 00:01:36,820 --> 00:01:39,970 Now the bank servers still believe there's an authentication 47 47 00:01:39,970 --> 00:01:42,510 that has happened between the client and the bank servers. 48 48 00:01:42,510 --> 00:01:44,460 So they're going to process the requests 49 49 00:01:44,460 --> 00:01:47,210 and instead they're going be sending 100 times the money 50 50 00:01:47,210 --> 00:01:48,590 from the client's checking account 51 51 00:01:48,590 --> 00:01:49,710 to the attacker's account, 52 52 00:01:49,710 --> 00:01:52,620 as directed by this modified request they received. 53 53 00:01:52,620 --> 00:01:54,660 Now another type of general network attack 54 54 00:01:54,660 --> 00:01:56,500 is known as session hijacking. 55 55 00:01:56,500 --> 00:01:58,600 Session hijacking occurs when an attacker 56 56 00:01:58,600 --> 00:02:00,890 is able to guess the session ID that is in use 57 57 00:02:00,890 --> 00:02:02,500 between a client and a server, 58 58 00:02:02,500 --> 00:02:04,340 and then they could try to take over 59 59 00:02:04,340 --> 00:02:06,280 that already authenticated session. 60 60 00:02:06,280 --> 00:02:07,470 In this type of attack, 61 61 00:02:07,470 --> 00:02:09,580 it's very similar to an on-path attack, 62 62 00:02:09,580 --> 00:02:11,460 but instead of being placed into the middle 63 63 00:02:11,460 --> 00:02:13,800 of the conversation and relaying the victim's request 64 64 00:02:13,800 --> 00:02:14,633 to the server, 65 65 00:02:14,633 --> 00:02:17,430 it instead focuses on taking over the session completely 66 66 00:02:17,430 --> 00:02:19,560 and the victim's machine is no longer receiving 67 67 00:02:19,560 --> 00:02:20,900 any of the data. 68 68 00:02:20,900 --> 00:02:23,200 This type of attack is focused on exploiting the way 69 69 00:02:23,200 --> 00:02:26,210 TCP/IP protocols are going to use session numbers 70 70 00:02:26,210 --> 00:02:29,500 or session IDs at layer five of the OSI model. 71 71 00:02:29,500 --> 00:02:31,400 In the early days of TCP/IP, 72 72 00:02:31,400 --> 00:02:33,710 the session IDs were not randomly assigned, 73 73 00:02:33,710 --> 00:02:36,200 but instead they were assigned in sequential order. 74 74 00:02:36,200 --> 00:02:38,800 So if I had session ID 123, 75 75 00:02:38,800 --> 00:02:40,620 I could probably guess that your next session 76 76 00:02:40,620 --> 00:02:42,470 was going to be 124, 77 77 00:02:42,470 --> 00:02:44,410 and if you create your session right before, 78 78 00:02:44,410 --> 00:02:48,770 or right after me, I can then guess your ID as 122 or 124, 79 79 00:02:48,770 --> 00:02:52,410 because it's one before or one after my particular session. 80 80 00:02:52,410 --> 00:02:53,940 So to combat this, 81 81 00:02:53,940 --> 00:02:56,820 session ID's now got to be randomized 82 82 00:02:56,820 --> 00:02:59,630 inside our newer TCP/IP configurations. 83 83 00:02:59,630 --> 00:03:01,970 So if I now have session 123, 84 84 00:03:01,970 --> 00:03:06,130 you might have session 934, or 523 or anything else, really, 85 85 00:03:06,130 --> 00:03:08,330 because it's going to be just randomly assigned to you 86 86 00:03:08,330 --> 00:03:10,520 and that way I can't guess your session ID 87 87 00:03:10,520 --> 00:03:13,800 and take over your session using session hijacking. 88 88 00:03:13,800 --> 00:03:17,250 Next, we're going to discuss an attack known as DNS poisoning. 89 89 00:03:17,250 --> 00:03:19,890 Now, DNS poisoning occurs when an attacker manipulates 90 90 00:03:19,890 --> 00:03:22,600 known vulnerabilities within the domain name system, 91 91 00:03:22,600 --> 00:03:25,580 or DNS, to reroute traffic from one site 92 92 00:03:25,580 --> 00:03:27,690 to a fake version of that site. 93 93 00:03:27,690 --> 00:03:30,860 DNS poisoning usually occurs on a company's internal DNS 94 94 00:03:30,860 --> 00:03:33,500 servers instead of on the public facing DNS servers 95 95 00:03:33,500 --> 00:03:35,690 used by most of us on the internet. 96 96 00:03:35,690 --> 00:03:38,310 But in some cases, those internet DNS servers 97 97 00:03:38,310 --> 00:03:39,930 have also been poisoned. 98 98 00:03:39,930 --> 00:03:43,430 Remember DNS is used for one big thing. 99 99 00:03:43,430 --> 00:03:45,980 It's to be able to provide a method of changing domain names 100 100 00:03:45,980 --> 00:03:48,370 into IP addresses and vice versa. 101 101 00:03:48,370 --> 00:03:49,920 When a client needs to go to a website 102 102 00:03:49,920 --> 00:03:51,410 like diontraining.com, 103 103 00:03:51,410 --> 00:03:53,930 they asked their DNS server for the location of that server, 104 104 00:03:53,930 --> 00:03:56,910 and they receive an IP address back as the location 105 105 00:03:56,910 --> 00:03:58,270 from that DNS server 106 106 00:03:58,270 --> 00:04:00,350 and then their computer goes to the IP address 107 107 00:04:00,350 --> 00:04:01,630 to load the website. 108 108 00:04:01,630 --> 00:04:04,130 Now, since DNS works in a hierarchal manner, 109 109 00:04:04,130 --> 00:04:05,930 the client assets local DNS servers 110 110 00:04:05,930 --> 00:04:08,050 for the resolution of that domain first. 111 111 00:04:08,050 --> 00:04:09,880 If the DNS server has the domain name 112 112 00:04:09,880 --> 00:04:12,110 and IP address stored locally within its cache, 113 113 00:04:12,110 --> 00:04:14,390 it's going to return that address to the client. 114 114 00:04:14,390 --> 00:04:17,630 So what does an attacker do in DNS poisoning? 115 115 00:04:17,630 --> 00:04:20,040 Well, they're going to attempt to change the IP address 116 116 00:04:20,040 --> 00:04:22,400 of a domain name stored in the DNS cache 117 117 00:04:22,400 --> 00:04:24,120 of a given DNS server. 118 118 00:04:24,120 --> 00:04:26,630 If they can do that, any client who requests to visit 119 119 00:04:26,630 --> 00:04:27,930 that website in the future 120 120 00:04:27,930 --> 00:04:30,840 will be redirected to a website controlled by the attacker, 121 121 00:04:30,840 --> 00:04:32,800 allowing them to conduct further exploitation 122 122 00:04:32,800 --> 00:04:35,300 of your client, which is now their victim. 123 123 00:04:35,300 --> 00:04:37,830 Remember, DNS poisoning works by poisoning 124 124 00:04:37,830 --> 00:04:40,500 either a workstation or servers DNS cache, 125 125 00:04:40,500 --> 00:04:42,320 hijacking their local DNS server 126 126 00:04:42,320 --> 00:04:44,780 or performing an unauthorized zone transfer 127 127 00:04:44,780 --> 00:04:47,660 to an unpatched DNS server to change the IP address 128 128 00:04:47,660 --> 00:04:49,750 of a given web servers A record. 129 129 00:04:49,750 --> 00:04:51,820 To counteract DNS poisoning attacks, 130 130 00:04:51,820 --> 00:04:55,878 a secure version of DNS known as DNSSEC has been created. 131 131 00:04:55,878 --> 00:04:58,160 DNSSEC uses encrypted digital signatures 132 132 00:04:58,160 --> 00:05:00,500 when passing DNS information between servers 133 133 00:05:00,500 --> 00:05:02,210 to help protect it from poisoning. 134 134 00:05:02,210 --> 00:05:04,690 You can also prevent your DNS servers from being poisoned 135 135 00:05:04,690 --> 00:05:07,280 by ensuring your server has the latest security patches 136 136 00:05:07,280 --> 00:05:08,920 and the latest updates to make sure 137 137 00:05:08,920 --> 00:05:10,970 they're always properly protected. 138 138 00:05:10,970 --> 00:05:12,510 The next attack we're going to discuss 139 139 00:05:12,510 --> 00:05:15,230 involves the use of rogue DHCP servers. 140 140 00:05:15,230 --> 00:05:18,470 Now a rogue DHCP server is any DHCP server 141 141 00:05:18,470 --> 00:05:19,900 that is connected to your network, 142 142 00:05:19,900 --> 00:05:21,820 but you as the network administrator 143 143 00:05:21,820 --> 00:05:24,850 did not have control over and did not install it. 144 144 00:05:24,850 --> 00:05:27,500 This usually happens when an attacker or an end user 145 145 00:05:27,500 --> 00:05:29,990 connects their own DHCP server to your network, 146 146 00:05:29,990 --> 00:05:33,340 and often it's unintentionally done by your own users. 147 147 00:05:33,340 --> 00:05:36,020 When that rogue DHCP servers connected to the network, 148 148 00:05:36,020 --> 00:05:38,150 it's going to do what DHCP servers do 149 149 00:05:38,150 --> 00:05:40,020 and it's going to start assigning IPs to clients 150 150 00:05:40,020 --> 00:05:41,550 on the network when they boot up 151 151 00:05:41,550 --> 00:05:43,120 and reconnect to the network. 152 152 00:05:43,120 --> 00:05:45,640 Now, the issue here is that these rogue DHCP servers 153 153 00:05:45,640 --> 00:05:49,190 are now handing out IP addresses, subnet masks, gateways, 154 154 00:05:49,190 --> 00:05:52,380 and DNS server assignments to your network clients. 155 155 00:05:52,380 --> 00:05:53,220 In the best case, 156 156 00:05:53,220 --> 00:05:55,680 these rogue DHCP servers are simply going to be connected 157 157 00:05:55,680 --> 00:05:56,970 by one of your end users 158 158 00:05:56,970 --> 00:05:58,840 because they wanted to add a wireless access point 159 159 00:05:58,840 --> 00:06:00,310 to their office and so they ran down 160 160 00:06:00,310 --> 00:06:02,280 to the local electronics store and they bought themselves 161 161 00:06:02,280 --> 00:06:03,930 a wireless router or gateway. 162 162 00:06:03,930 --> 00:06:07,070 Little did they know these devices include a DHCP server 163 163 00:06:07,070 --> 00:06:08,470 that's turned on by default. 164 164 00:06:08,470 --> 00:06:10,000 So when they connected it to the network, 165 165 00:06:10,000 --> 00:06:13,450 it began its job as handing out DHCP server addresses. 166 166 00:06:13,450 --> 00:06:15,450 This can lead to clients that have the same IP address 167 167 00:06:15,450 --> 00:06:18,360 as other clients in the network because this DHCP server 168 168 00:06:18,360 --> 00:06:20,670 is rogue and it doesn't know what addresses 169 169 00:06:20,670 --> 00:06:23,040 your official DHCP server was already using 170 170 00:06:23,040 --> 00:06:24,570 inside that same scope. 171 171 00:06:24,570 --> 00:06:27,640 This is especially popular inside private class C addresses 172 172 00:06:27,640 --> 00:06:31,200 of 192.168.1.0/24. 173 173 00:06:31,200 --> 00:06:34,160 And this can lead to two clients having connectivity issues 174 174 00:06:34,160 --> 00:06:37,250 on the network because they both have the same IP address. 175 175 00:06:37,250 --> 00:06:38,370 Now, in the worst case, 176 176 00:06:38,370 --> 00:06:40,900 this rogue DHCP server was actually attached to your network 177 177 00:06:40,900 --> 00:06:41,900 by an attacker. 178 178 00:06:41,900 --> 00:06:43,880 The attacker could then issue out IP addresses 179 179 00:06:43,880 --> 00:06:46,740 and subnet mask that will properly connect to your network. 180 180 00:06:46,740 --> 00:06:49,700 But these rogue DHCP servers can also be used 181 181 00:06:49,700 --> 00:06:51,500 to configure clients to use a gateway 182 182 00:06:51,500 --> 00:06:52,890 that the attacker controls, 183 183 00:06:52,890 --> 00:06:55,170 and this would allow them to do an on-path attack 184 184 00:06:55,170 --> 00:06:57,310 and intercept or modify communications 185 185 00:06:57,310 --> 00:06:59,640 between the clients and the outside servers. 186 186 00:06:59,640 --> 00:07:01,360 This essentially becomes an on-path 187 187 00:07:01,360 --> 00:07:02,860 or Man in the Middle attack. 188 188 00:07:02,860 --> 00:07:04,810 These rogue DHCP servers can also assign 189 189 00:07:04,810 --> 00:07:06,980 a different DNS server for the clients to use. 190 190 00:07:06,980 --> 00:07:09,950 This can effectively create the same effect as DNS poisoning 191 191 00:07:09,950 --> 00:07:11,330 from the client's perspective. 192 192 00:07:11,330 --> 00:07:13,950 So you want to be wary of these rogue DHCP servers, 193 193 00:07:13,950 --> 00:07:15,410 and always look for them on your network 194 194 00:07:15,410 --> 00:07:17,860 and when you find them, get them off the network. 195 195 00:07:19,023 --> 00:07:21,220 (static whooshing)