1 00:00:01,720 --> 00:00:07,830 Welcome to a lecture on the security of operating systems the first module in the series will focus 2 00:00:07,830 --> 00:00:13,210 on operating system security models illustrated by Windows systems. 3 00:00:13,250 --> 00:00:18,020 We will try and answer the following question what level of protection can be offered by an operating 4 00:00:18,020 --> 00:00:18,910 system. 5 00:00:21,520 --> 00:00:24,330 Let's start with basic security. 6 00:00:24,360 --> 00:00:27,270 What sort of protection can be expected from operating systems 7 00:00:30,810 --> 00:00:35,560 an operating system must above all guarantee the availability of provided services. 8 00:00:37,080 --> 00:00:41,560 We as users need to be sure that the tasks we want to execute will be executed. 9 00:00:43,480 --> 00:00:48,250 We also need to be sure that the system performance will be reliable for example that the system will 10 00:00:48,250 --> 00:00:48,920 not fail 11 00:00:51,710 --> 00:00:56,690 and the aspect that is most relevant in this course is that the data is stored and processed by an operating 12 00:00:56,690 --> 00:01:02,000 system will remain secure and confidential and that its integrity won't be compromised. 13 00:01:04,430 --> 00:01:12,370 Modern operating systems or any of the computers we're used are almost always connected to some network. 14 00:01:12,400 --> 00:01:15,930 There are also almost always connected to the global network the Internet 15 00:01:18,870 --> 00:01:24,010 their environment supports a number of applications which exchange data with external services without 16 00:01:24,010 --> 00:01:24,860 her knowledge. 17 00:01:27,160 --> 00:01:32,380 This is a problem because we have no control or little control over the data that can be found in our 18 00:01:32,380 --> 00:01:34,340 computer and is processed by it. 19 00:01:39,340 --> 00:01:44,210 A good example of this are any viruses or any other programs that update regularly 20 00:01:46,810 --> 00:01:52,180 some developers set the default control to such an aggressive level that an anti-virus checks for virus 21 00:01:52,180 --> 00:01:59,450 database updates multiple times per minute if you monitor network traffic you'll see that your scanner 22 00:01:59,450 --> 00:02:04,060 sends out an update query regularly even every 15 or 20 seconds. 23 00:02:10,750 --> 00:02:16,450 To standardize the security that is provided by a computer system a classification for evaluating security 24 00:02:16,450 --> 00:02:20,070 levels has been introduced. 25 00:02:20,220 --> 00:02:25,320 Initially the assessment criteria of operating system security were published in a document called the 26 00:02:25,320 --> 00:02:28,300 Orange Book. 27 00:02:28,360 --> 00:02:32,410 It was part of a rainbow book series on computer systems security. 28 00:02:32,410 --> 00:02:38,910 Several years later the evaluation standard was updated and systematized. 29 00:02:38,950 --> 00:02:43,450 Today the binding standards are the common criteria for information technology. 30 00:02:43,510 --> 00:02:51,480 The CC norm as you can see there are several standard categories. 31 00:02:51,500 --> 00:02:56,600 The table above shows relationships or the corresponding security levels under the Orange Book and the 32 00:02:56,600 --> 00:03:02,010 Common Criteria standards. 33 00:03:02,020 --> 00:03:04,370 Let's start with the most basic systems. 34 00:03:04,420 --> 00:03:07,460 This is the division or the first e-mail level 35 00:03:10,250 --> 00:03:15,480 to be classified at this level an operating system doesn't have to offer any guarantee of protection. 36 00:03:17,730 --> 00:03:22,570 The system doesn't support for example the separation of user sessions. 37 00:03:22,580 --> 00:03:28,020 This means that the physical address to the computer means defacto gaining full control over the system. 38 00:03:30,780 --> 00:03:39,100 This includes the ability to open and modify other users data to give you an example the Windows 9x 39 00:03:39,100 --> 00:03:41,750 serious systems are classified at this level. 40 00:03:44,060 --> 00:03:49,700 The second level provides for discretionary data protection a system is required to authenticate an 41 00:03:49,700 --> 00:03:58,370 authorized users in a secure manner once identification is completed prior to executing each command. 42 00:03:58,470 --> 00:04:01,880 A user will be verified for having appropriate privileges to run it. 43 00:04:04,190 --> 00:04:09,840 Early Linux and Unix systems are classified at this level. 44 00:04:10,070 --> 00:04:16,240 The third level systems enforce access control adding to the features supported in level two systems 45 00:04:16,660 --> 00:04:23,930 systems classified at this level are required to provide for user activity monitoring each allowed or 46 00:04:23,930 --> 00:04:26,320 disallowed operation has to be logged. 47 00:04:28,770 --> 00:04:32,220 An example of a system class at this division is Windows A.E. 48 00:04:35,010 --> 00:04:41,370 the fourth level is restricted to systems that support labelled security protection. 49 00:04:41,420 --> 00:04:44,360 It's an implementation of a model known in cryptography. 50 00:04:44,360 --> 00:04:50,920 The security theory has the bell Lapa doula model will come back to this in the future. 51 00:04:52,820 --> 00:04:59,290 In a nutshell the model assigns sensitivity levels for certain types of data. 52 00:04:59,490 --> 00:05:04,530 A person with a given level of privileges will be able to access only the data that was assigned to 53 00:05:04,530 --> 00:05:07,330 the corresponding or lower sensitivity label. 54 00:05:09,870 --> 00:05:17,510 Newer Windows and Linux systems are classed at this level the fifth level also enforces structured protection 55 00:05:20,140 --> 00:05:24,910 it requires the operating system structure to allow for the monitoring and control of all operations 56 00:05:25,000 --> 00:05:26,860 executed by the system. 57 00:05:29,360 --> 00:05:33,770 This means that the uncontrollable tampering with data of another process is impossible. 58 00:05:35,340 --> 00:05:43,940 All launched operations are atomic operations and the access to the data processed by it must be authorized. 59 00:05:43,990 --> 00:05:47,200 The fifth level doesn't encompass popular operating systems. 60 00:05:48,180 --> 00:05:49,840 They don't even aspire to it. 61 00:05:52,900 --> 00:06:00,240 Some specialized versions of systems implemented on specific machines may be classed at this level. 62 00:06:00,410 --> 00:06:04,250 The six level systems required the provision of process isolation 63 00:06:06,930 --> 00:06:11,350 each security critical operation must be separate and independent in the system. 64 00:06:13,600 --> 00:06:19,060 The highest level the seventh level is assigned to those systems that are able to formally for example 65 00:06:19,060 --> 00:06:26,790 mathematically verify their security the systems have to effectively exclude any possibility of successful 66 00:06:26,790 --> 00:06:27,650 attacks. 67 00:06:32,790 --> 00:06:36,930 The security of these systems can't depend on configuration or user behavior. 68 00:06:38,240 --> 00:06:41,040 It has to offer formal assurance of full protection. 69 00:06:42,190 --> 00:06:47,190 Level 7 encompasses several devices not systems. 70 00:06:47,220 --> 00:06:50,040 They're definitely not commercially available. 71 00:06:50,040 --> 00:06:56,140 The modules that deal with operating systems security will talk above all about systems security boundaries. 72 00:06:58,320 --> 00:07:03,180 The concept of a security boundary is vitally important as safeguarding a system against cyber threats 73 00:07:03,180 --> 00:07:09,810 amounts to risk management we've realized this early on during the first modules of the first part of 74 00:07:09,810 --> 00:07:15,400 our course to manage the risks in a conscious manner. 75 00:07:15,650 --> 00:07:22,840 You have to be aware of the protection that is offered by a computer system. 76 00:07:22,870 --> 00:07:27,740 You also need to take note of the fact that an operating system can only protect data when it's running. 77 00:07:28,880 --> 00:07:34,410 It doesn't protect data against local attacks. 78 00:07:34,490 --> 00:07:39,260 We'll try to give you hints on using popular operating systems in a considerably security conscious 79 00:07:39,260 --> 00:07:39,930 way. 80 00:07:42,540 --> 00:07:47,310 And finally we'll also take a look at the concept of granting rights to users. 81 00:07:47,310 --> 00:07:54,220 What did the programs launched by users this different security model's been supported for many years 82 00:07:54,220 --> 00:07:59,370 and many computer systems also in Windows systems. 83 00:07:59,580 --> 00:08:05,610 The security model we just mentioned a model that is based on code on access rights is on the shelf 84 00:08:05,640 --> 00:08:08,060 but seldom used. 85 00:08:08,060 --> 00:08:12,710 This means that it's the task of the administrator to stop users from launching any potentially harmful 86 00:08:12,710 --> 00:08:13,850 programs. 87 00:08:16,130 --> 00:08:21,290 In the next lecture of this series we'll learn about the implementation of this. 88 00:08:21,330 --> 00:08:26,240 We'll also take a look at the techniques and tools for independent detection and removal of malware. 89 00:08:27,470 --> 00:08:34,190 The malware we refer to are mostly root kits programs that attempt to hide from users and administrators. 90 00:08:35,170 --> 00:08:41,750 At the end will evaluate the security of our systems configuration errors are in practice the largest 91 00:08:41,750 --> 00:08:48,550 source of problems with the protection measures effectiveness users and administrators often don't modify 92 00:08:48,550 --> 00:08:54,520 the default configuration of living it's set to provide the highest security which is not true. 93 00:08:55,440 --> 00:09:02,530 Or sometimes reconfigure their systems in a way that lowers the security even further. 94 00:09:02,540 --> 00:09:03,500 See you in the training.