1 00:00:02,510 --> 00:00:11,990 Walk into the lecture and title defense depth security model this is a strategy developed by the military. 2 00:00:12,080 --> 00:00:17,840 The idea behind it is that instead of defeating an attacker with a single strong defensive line it's 3 00:00:17,840 --> 00:00:22,350 better to weaken the attack by forcing the attacker to overcome successive barriers. 4 00:00:24,450 --> 00:00:31,220 You spread out the security for example by doubling protective measures so that it covers a relatively 5 00:00:31,220 --> 00:00:40,740 large space even if the first line of defense falls and even if the second follows the attack will become 6 00:00:40,740 --> 00:00:47,150 noticeable and will lose momentum which will buy time to react appropriately. 7 00:00:47,190 --> 00:00:50,320 The same strategy can be applied to computer systems as well. 8 00:00:58,330 --> 00:01:04,240 Computer systems should be viewed in the way presented in the diagram on the right of the slide. 9 00:01:04,320 --> 00:01:10,090 It presents a system based on independent function layers. 10 00:01:10,240 --> 00:01:15,770 We will analyze each layer in detail later on. 11 00:01:15,820 --> 00:01:19,450 Please note that every layer takes into account the human factor. 12 00:01:20,150 --> 00:01:23,630 It's the most critical factor that affects security of the whole system. 13 00:01:24,930 --> 00:01:28,130 People are very often the weakest link in the security of the system. 14 00:01:30,340 --> 00:01:35,710 Users are susceptible to social engineering and manipulation. 15 00:01:35,730 --> 00:01:38,950 We will now describe the defense and death model in more detail. 16 00:01:40,650 --> 00:01:43,920 Let's try to illustrate it outside the world of computers. 17 00:01:45,030 --> 00:01:48,860 Some medieval castles were surrounded by a moat. 18 00:01:48,880 --> 00:01:51,790 The point was to make the enemy approach the barrier. 19 00:01:52,150 --> 00:01:58,350 The castle was usually protected by one mode only such defenses weren't duplicated. 20 00:01:59,320 --> 00:02:04,960 There was no point in doing that because if the enemy was able to defeat the barrier once they'd be 21 00:02:04,960 --> 00:02:06,380 able to do it again. 22 00:02:08,760 --> 00:02:12,390 Behind the moat there was a wall. 23 00:02:12,470 --> 00:02:18,120 It was an additional barrier independent of the previous one. 24 00:02:18,200 --> 00:02:23,720 Even if somebody managed to cross the moat they couldn't use the same strategy to climb up the wall. 25 00:02:26,190 --> 00:02:31,890 The basis of the defense and depth model is that individual layers of security and solutions implemented 26 00:02:31,890 --> 00:02:34,590 in each layer work independently of one another. 27 00:02:36,930 --> 00:02:42,620 Having three different virus scanners is not exactly a defense in depth. 28 00:02:42,740 --> 00:02:47,720 You can't assume that 3 scanners are better than one because if one doesn't detect a threat another 29 00:02:47,720 --> 00:02:48,320 one will 30 00:02:51,000 --> 00:02:57,950 three anti-virus scanners are just as effective as one defensins that requires installation of three 31 00:02:57,950 --> 00:03:05,210 solutions independent of one another very often money is spent on duplicating security measures for 32 00:03:05,210 --> 00:03:12,610 every layer of the system whereas each layer can be sufficiently protected by only one solution. 33 00:03:13,890 --> 00:03:21,120 This is true also with regards to users. 34 00:03:21,170 --> 00:03:26,180 We will analyze the model from top to bottom starting from data and application layers. 35 00:03:28,190 --> 00:03:30,700 How can you secure data stored in computer systems 36 00:03:33,440 --> 00:03:35,550 access control is the first solution. 37 00:03:37,250 --> 00:03:42,850 This involves granting users access privileges. 38 00:03:42,890 --> 00:03:48,560 The second solution which should be complementary to the first one is to prevent data loss by means 39 00:03:48,560 --> 00:03:50,780 described in the service license agreement 40 00:03:53,520 --> 00:03:59,170 this entails making backup copies or replicating data. 41 00:03:59,190 --> 00:04:06,090 The next solution is to monitor data access you have to know who and when tried to read and modify the 42 00:04:06,090 --> 00:04:08,730 data and whether they succeeded. 43 00:04:11,320 --> 00:04:18,940 All in all data encryption is the only complete effective solution ensuring data confidentiality. 44 00:04:19,060 --> 00:04:23,410 It makes the data independent of the system it's stored in and processed by 45 00:04:26,330 --> 00:04:33,110 the first element of application layer protection is to regularly update your applications. 46 00:04:33,160 --> 00:04:40,230 It will only be possible if the administrator knows every application running on the system. 47 00:04:40,240 --> 00:04:45,150 This means he or she cannot allow users to install on their computers any application they want. 48 00:04:46,910 --> 00:04:50,060 If you don't know something exists you won't try to update it. 49 00:04:52,430 --> 00:04:58,380 Application updates are much more difficult to control than whole system updates. 50 00:04:58,460 --> 00:05:02,230 It's hard to make it automatic. 51 00:05:02,270 --> 00:05:05,970 The administrator has to remember to regularly update all applications 52 00:05:08,580 --> 00:05:10,440 to implement the rules described above. 53 00:05:10,440 --> 00:05:14,190 The administrator may prevent users from installing any kind of software 54 00:05:17,590 --> 00:05:22,770 the administrator may introduce security measures that won't allow any user to install a certain program 55 00:05:25,240 --> 00:05:30,360 this approach differentiates between allowed and forbidden programs. 56 00:05:30,380 --> 00:05:35,970 It's a mechanism completely independent of user privileges. 57 00:05:35,990 --> 00:05:39,850 Of course this layer should also be protected by anti-virus software.