1 00:00:02,280 --> 00:00:06,090 This lecture will be devoted to protocols and networking. 2 00:00:06,280 --> 00:00:13,500 We'll analyze the three lowest layers of the S.I. model. 3 00:00:13,530 --> 00:00:15,170 We'll start with a physical layer. 4 00:00:18,480 --> 00:00:24,190 The security risk that the physical layer is most susceptible to comes from the denial of service attack. 5 00:00:24,660 --> 00:00:29,270 The result of this attack is the authorized users cannot use certain systems services 6 00:00:32,010 --> 00:00:36,680 as we know the physical layer is the basis of all higher layers. 7 00:00:36,720 --> 00:00:39,960 It's easy to conduct a successful attack on the physical layer. 8 00:00:42,420 --> 00:00:45,860 Unfortunately few technological solutions can prevent that. 9 00:00:49,570 --> 00:00:52,710 The piece of news that you see in the slide provides a good example. 10 00:00:55,240 --> 00:01:00,100 The story is about a 75 year old Georgian woman who cut off most of our mania from the internet. 11 00:01:02,880 --> 00:01:04,660 Scavenging for scrap metal. 12 00:01:04,770 --> 00:01:07,110 She found a transmission cable. 13 00:01:07,110 --> 00:01:10,780 She thought it was a copper cable but it turned out to be a fiber optic cable. 14 00:01:12,440 --> 00:01:15,820 Obviously she didn't manage to get even $25 for it. 15 00:01:17,290 --> 00:01:22,150 From our perspective the most important bit of this story is the woman managed to defeat the security 16 00:01:22,150 --> 00:01:25,580 measures of all the computers in our mania with a shovel. 17 00:01:28,300 --> 00:01:31,700 DNS attacks are a serious vulnerability of the physical layer. 18 00:01:33,500 --> 00:01:39,290 Wireless networks are especially susceptible to this problem but this will be the topic of another lecture. 19 00:01:48,300 --> 00:01:55,330 The second serious vulnerability of the physical layer comes from unauthorized access to the medium. 20 00:01:55,430 --> 00:01:59,660 The picture you see above shows that you shouldn't blindly follow stereotypes. 21 00:02:01,390 --> 00:02:07,170 One such stereotype is that fiber optic cable connection is always more secure than a copper cable connection. 22 00:02:09,440 --> 00:02:14,570 It's generally accepted that a copper cable signal is easy to intercept because the transmission emits 23 00:02:14,630 --> 00:02:18,810 an electromagnetic field. 24 00:02:18,810 --> 00:02:24,660 Moreover many people think that a fiber optic cable transmits lightwaves which are immune to electromagnetic 25 00:02:24,660 --> 00:02:31,310 interference and thus the signal cannot be intercepted without cutting across the cable. 26 00:02:31,370 --> 00:02:33,520 And this in turn can be easily detected. 27 00:02:35,870 --> 00:02:37,560 This is not entirely true. 28 00:02:39,900 --> 00:02:42,810 The device you see in the slide is widely available on the Internet. 29 00:02:43,670 --> 00:02:48,530 It costs about $1000 if you can access the fiber physically. 30 00:02:48,900 --> 00:02:53,060 You have to bend it in such a way that you see in the picture and attach it to the device. 31 00:02:53,840 --> 00:02:57,140 After that the fiber emits wave light outside. 32 00:02:59,330 --> 00:03:05,900 When the light gets reflected from the wall of the cable the light loss is about 1 percent a sensitive 33 00:03:05,900 --> 00:03:10,320 detector could intercept the signal escaping from the fiber. 34 00:03:10,410 --> 00:03:17,660 Then you just have to convert the signal back to the electric form and connected device to the computer. 35 00:03:17,700 --> 00:03:24,180 That's how you get an optical fiber cable monitoring system. 36 00:03:24,200 --> 00:03:27,590 Of course there are devices that can detect that the fiber is bent. 37 00:03:29,170 --> 00:03:34,810 If there's an automated attack someone has probably already invested money to develop an automated defense 38 00:03:34,810 --> 00:03:36,050 against the attack. 39 00:03:37,510 --> 00:03:46,050 However the devices for the signal interception monitoring costs much more than a thousand dollars. 40 00:03:46,190 --> 00:03:51,380 If someone can get physical access to the medium through which the signal is sent that can intercept 41 00:03:51,410 --> 00:03:55,670 all the data that passes through that medium. 42 00:03:55,840 --> 00:04:00,450 In many cases they can also modify it in real time. 43 00:04:00,550 --> 00:04:05,830 For example the moment it was sent the data at the far end of the fiber is different from that which 44 00:04:05,830 --> 00:04:14,700 was sent for example your subtotal might have changed or a piece of hostile code was added to the binary 45 00:04:14,700 --> 00:04:15,730 file. 46 00:04:15,930 --> 00:04:17,810 You should trust the data source. 47 00:04:18,850 --> 00:04:23,990 However after the data passed through a medium that was accessed by an unauthorized person. 48 00:04:24,280 --> 00:04:30,200 The end result may be different from the one expected such attacks represent a serious risk for modern 49 00:04:30,200 --> 00:04:31,510 computer systems. 50 00:04:32,960 --> 00:04:41,390 No medium ensures protection against data interception. 51 00:04:41,540 --> 00:04:47,600 The physical layer doesn't provide any technology that would allow data encryption nor does it include 52 00:04:47,600 --> 00:04:52,370 any solution that would enable the receiver to authenticate the sender of the data package. 53 00:04:56,160 --> 00:05:02,250 The two main threats the physical layer is susceptible to come from DNS attacks which can be as simple 54 00:05:02,250 --> 00:05:07,820 as unplugging a network cable and interception and modification of the data sent through the medium 55 00:05:09,860 --> 00:05:11,500 without the use of technology. 56 00:05:11,510 --> 00:05:16,140 You have to restrict access to the medium to do so. 57 00:05:16,140 --> 00:05:21,130 Companies employ security firms install digital locks et cetera. 58 00:05:23,110 --> 00:05:30,240 Monitoring the surroundings of the company's premises may also provide effective protection consequences 59 00:05:30,240 --> 00:05:34,360 of a malfunction can be limited by duplicating the most important connections. 60 00:05:37,290 --> 00:05:40,990 But these are the only three available methods of physical layer protection.