1 1 00:00:00,150 --> 00:00:02,310 Malware exploitation. 2 2 00:00:02,310 --> 00:00:03,930 In this lesson, we're going to talk 3 3 00:00:03,930 --> 00:00:06,360 about malware exploitation techniques, 4 4 00:00:06,360 --> 00:00:10,020 and so we have to first define what is an exploit technique? 5 5 00:00:10,020 --> 00:00:12,900 Well, an exploit technique describes the specific method 6 6 00:00:12,900 --> 00:00:16,230 by which malware code infects a targeted host. 7 7 00:00:16,230 --> 00:00:19,230 Now, there is lots of different ways that this can be done. 8 8 00:00:19,230 --> 00:00:21,870 In the old days, we used to have malware that would go 9 9 00:00:21,870 --> 00:00:23,670 and rewrite or modify the code 10 10 00:00:23,670 --> 00:00:27,390 within an executable or a macro file on a target disk. 11 11 00:00:27,390 --> 00:00:30,510 That way, whenever that file was run, the virus was loaded, 12 12 00:00:30,510 --> 00:00:34,230 it could execute its payload and go out and do bad things. 13 13 00:00:34,230 --> 00:00:35,430 Now, if you had worm malware, 14 14 00:00:35,430 --> 00:00:38,370 it would actually go out and try to infect only the memory, 15 15 00:00:38,370 --> 00:00:39,750 and then go through a process 16 16 00:00:39,750 --> 00:00:41,430 of going through remote procedure calls 17 17 00:00:41,430 --> 00:00:43,620 over the network, trying to infect as many other hosts 18 18 00:00:43,620 --> 00:00:44,850 as it could. 19 19 00:00:44,850 --> 00:00:46,680 Now, modern malware, on the other hand though, 20 20 00:00:46,680 --> 00:00:49,380 uses fileless techniques to avoid detection 21 21 00:00:49,380 --> 00:00:50,970 by signature-based security systems 22 22 00:00:50,970 --> 00:00:54,690 like antivirus and host-based intrusion detection systems. 23 23 00:00:54,690 --> 00:00:55,800 By being fileless, 24 24 00:00:55,800 --> 00:00:59,460 this means that the malware is executed directly as a script 25 25 00:00:59,460 --> 00:01:02,460 or a small piece of shell code that creates a process 26 26 00:01:02,460 --> 00:01:04,470 in the system memory without having to use 27 27 00:01:04,470 --> 00:01:06,120 the local file system. 28 28 00:01:06,120 --> 00:01:08,040 Now, some of these things will actually get installed 29 29 00:01:08,040 --> 00:01:10,440 to a temporary directory first, and then be run, 30 30 00:01:10,440 --> 00:01:11,910 and then they'll delete themselves. 31 31 00:01:11,910 --> 00:01:14,400 But we'll still consider those relatively fileless 32 32 00:01:14,400 --> 00:01:16,500 because there's not a lot of evidence on the drive 33 33 00:01:16,500 --> 00:01:18,060 for people to find you. 34 34 00:01:18,060 --> 00:01:20,700 Now, this is one of the things that a lot of APTs will use, 35 35 00:01:20,700 --> 00:01:23,790 and so we have to ask the question is how does an APT 36 36 00:01:23,790 --> 00:01:26,190 use this modern malware to operate? 37 37 00:01:26,190 --> 00:01:29,340 Well, first, it's going to use a dropper or a downloader. 38 38 00:01:29,340 --> 00:01:32,400 The first step is the malware has to get on your computer, 39 39 00:01:32,400 --> 00:01:34,410 and it's going to do that in a fileless manner. 40 40 00:01:34,410 --> 00:01:35,370 And the way they're going to do this 41 41 00:01:35,370 --> 00:01:38,460 is by running lightweight shell code on your system. 42 42 00:01:38,460 --> 00:01:40,770 By doing this, this becomes what we call a dropper 43 43 00:01:40,770 --> 00:01:42,180 or a stage one dropper, 44 44 00:01:42,180 --> 00:01:44,820 and it's then going to go out and download the rest 45 45 00:01:44,820 --> 00:01:45,720 of the code. 46 46 00:01:45,720 --> 00:01:47,820 And so that dropper is just a very small file, 47 47 00:01:47,820 --> 00:01:50,100 and can run very easily from memory. 48 48 00:01:50,100 --> 00:01:52,350 Now, the whole point here is to try to trick the user 49 49 00:01:52,350 --> 00:01:54,660 into clicking on something or running the code, 50 50 00:01:54,660 --> 00:01:57,720 and that way, they are infecting their own machine. 51 51 00:01:57,720 --> 00:02:00,990 At that point, the APT then tries to maintain access. 52 52 00:02:00,990 --> 00:02:02,670 The malware is now on the system, 53 53 00:02:02,670 --> 00:02:05,340 and it's going to install that second stage downloader. 54 54 00:02:05,340 --> 00:02:06,780 That downloader can download something 55 55 00:02:06,780 --> 00:02:08,610 like a remote access Trojan, 56 56 00:02:08,610 --> 00:02:10,410 and this will give the adversary C2 57 57 00:02:10,410 --> 00:02:12,210 over that victim machine. 58 58 00:02:12,210 --> 00:02:14,670 After that, they're going to start strengthening their access. 59 59 00:02:14,670 --> 00:02:16,980 And to do that, they're going to use that remote access tool 60 60 00:02:16,980 --> 00:02:19,350 they have from the maintaining access phase, 61 61 00:02:19,350 --> 00:02:20,670 and they're going to start looking around 62 62 00:02:20,670 --> 00:02:23,250 and identifying and infecting other systems. 63 63 00:02:23,250 --> 00:02:25,020 As they're doing this, they're trying to find systems 64 64 00:02:25,020 --> 00:02:28,020 of higher values like servers or domain controllers. 65 65 00:02:28,020 --> 00:02:28,980 But even if not, 66 66 00:02:28,980 --> 00:02:30,960 they want to compromise other workstations too 67 67 00:02:30,960 --> 00:02:32,370 and do this lateral movement 68 68 00:02:32,370 --> 00:02:34,200 so they can gain additional privileges 69 69 00:02:34,200 --> 00:02:35,400 and an additional footprint. 70 70 00:02:35,400 --> 00:02:36,930 So if you find them on one machine, 71 71 00:02:36,930 --> 00:02:38,520 hopefully, you wouldn't find 'em on the other machine 72 72 00:02:38,520 --> 00:02:40,350 and they get to stay there. 73 73 00:02:40,350 --> 00:02:42,000 After this, they move into step four, 74 74 00:02:42,000 --> 00:02:44,010 which is actions on objectives. 75 75 00:02:44,010 --> 00:02:45,420 Now with actions on objectives, 76 76 00:02:45,420 --> 00:02:47,370 the attacker now has enough permissions, 77 77 00:02:47,370 --> 00:02:49,500 and they've identified enough things that are of interest 78 78 00:02:49,500 --> 00:02:51,450 that they can start doing what they want to do, 79 79 00:02:51,450 --> 00:02:53,940 which is usually going to be copying or stealing files, 80 80 00:02:53,940 --> 00:02:55,920 encrypting files, or doing something else, 81 81 00:02:55,920 --> 00:02:57,630 whatever their motive was. 82 82 00:02:57,630 --> 00:02:59,280 And then finally, we have our fifth step, 83 83 00:02:59,280 --> 00:03:00,600 which is concealment. 84 84 00:03:00,600 --> 00:03:02,880 The attacker at this point is going to maintain 85 85 00:03:02,880 --> 00:03:05,610 their tool access, but they might just go ahead 86 86 00:03:05,610 --> 00:03:07,200 and start hiding themself, 87 87 00:03:07,200 --> 00:03:08,790 and they're going to start covering their tracks 88 88 00:03:08,790 --> 00:03:11,250 by deleting log files and things like that. 89 89 00:03:11,250 --> 00:03:13,140 They want to make sure they're eradicating any sign 90 90 00:03:13,140 --> 00:03:15,690 that they were there, and that they infected your system. 91 91 00:03:15,690 --> 00:03:17,460 Because this way, they can stay there longer 92 92 00:03:17,460 --> 00:03:20,490 if they need to, and they can always go back in later on 93 93 00:03:20,490 --> 00:03:22,650 if they need to get something else from the machine. 94 94 00:03:22,650 --> 00:03:25,950 All right, so that is the basic five steps of an attack. 95 95 00:03:25,950 --> 00:03:27,360 And I mentioned a couple of terms there 96 96 00:03:27,360 --> 00:03:28,920 that I think we need to go back and define 97 97 00:03:28,920 --> 00:03:29,970 a little bit deeper. 98 98 00:03:29,970 --> 00:03:32,220 I talked about things like droppers and downloaders 99 99 00:03:32,220 --> 00:03:34,050 and shell codes and lots of other things. 100 100 00:03:34,050 --> 00:03:35,850 So let's take a look at those. 101 101 00:03:35,850 --> 00:03:37,440 First, we have a dropper. 102 102 00:03:37,440 --> 00:03:39,720 Now a dropper is a specialized type of malware 103 103 00:03:39,720 --> 00:03:42,570 that's designed to install or run other types of malware 104 104 00:03:42,570 --> 00:03:45,240 embedded in a payload on an infected host. 105 105 00:03:45,240 --> 00:03:46,950 Usually, this will be a stage one dropper 106 106 00:03:46,950 --> 00:03:48,660 as that code you first got. 107 107 00:03:48,660 --> 00:03:50,280 And once you get that code and run it, 108 108 00:03:50,280 --> 00:03:52,770 it's then going to go out and get some other code, 109 109 00:03:52,770 --> 00:03:55,050 and it uses a downloader to do that. 110 110 00:03:55,050 --> 00:03:57,120 Now, a downloader is a piece of code that connects 111 111 00:03:57,120 --> 00:03:59,190 to the internet to retrieve additional tools 112 112 00:03:59,190 --> 00:04:01,770 after the initial infection happens by a dropper. 113 113 00:04:01,770 --> 00:04:04,260 So often, we'll call this stage one for the dropper, 114 114 00:04:04,260 --> 00:04:06,870 stage two for the downloader. 115 115 00:04:06,870 --> 00:04:08,550 Now in my explanation of that process, 116 116 00:04:08,550 --> 00:04:10,440 I also mentioned the word shell code. 117 117 00:04:10,440 --> 00:04:12,510 Now, shell code is any lightweight code 118 118 00:04:12,510 --> 00:04:14,790 that's designed to run an exploit on a target. 119 119 00:04:14,790 --> 00:04:16,710 This can include any type of code format. 120 120 00:04:16,710 --> 00:04:18,150 It can be scripting languages, 121 121 00:04:18,150 --> 00:04:20,460 all the way down to a compiled binary. 122 122 00:04:20,460 --> 00:04:22,950 Now for the exam, I want you to remember, 123 123 00:04:22,950 --> 00:04:25,200 especially if you have some experience in the field, 124 124 00:04:25,200 --> 00:04:27,750 shell code originally referred to malware code. 125 125 00:04:27,750 --> 00:04:30,030 It would give the attacker a shell or a command prompt 126 126 00:04:30,030 --> 00:04:31,530 on the target system. 127 127 00:04:31,530 --> 00:04:32,940 And if you take the PenTest+ exam, 128 128 00:04:32,940 --> 00:04:34,650 that's how they're going to use that term. 129 129 00:04:34,650 --> 00:04:37,170 But here in CYSA for this exam, 130 130 00:04:37,170 --> 00:04:38,790 they want you to use the definition 131 131 00:04:38,790 --> 00:04:41,280 of the more generic shell code that I just provided, 132 132 00:04:41,280 --> 00:04:43,140 which is any lightweight code designed 133 133 00:04:43,140 --> 00:04:44,730 to run an exploit on a target. 134 134 00:04:44,730 --> 00:04:46,380 It doesn't have to give you a command prompt, 135 135 00:04:46,380 --> 00:04:48,450 it just has to be something that's going to give you 136 136 00:04:48,450 --> 00:04:50,910 some kind of an exploit that's going to be run. 137 137 00:04:50,910 --> 00:04:53,370 Now, once the shell code is created as a process 138 138 00:04:53,370 --> 00:04:55,830 on the target system, all this bad stuff 139 139 00:04:55,830 --> 00:04:57,450 has to start happening to your system, right? 140 140 00:04:57,450 --> 00:04:58,770 How does that happen? 141 141 00:04:58,770 --> 00:05:01,230 Well, one way is through code injection. 142 142 00:05:01,230 --> 00:05:03,240 Code injection is an exploit technique 143 143 00:05:03,240 --> 00:05:05,940 that runs malicious code with the identification number 144 144 00:05:05,940 --> 00:05:07,740 of a legitimate process. 145 145 00:05:07,740 --> 00:05:09,928 So when I go to install this code, 146 146 00:05:09,928 --> 00:05:12,180 and we're going to talk more about process exploring 147 147 00:05:12,180 --> 00:05:15,030 and how we can identify this type of behavior later on, 148 148 00:05:15,030 --> 00:05:16,530 you're going to notice that every process 149 149 00:05:16,530 --> 00:05:18,510 has a unique ID number with it. 150 150 00:05:18,510 --> 00:05:20,490 And so if I have something that is allowed to run 151 151 00:05:20,490 --> 00:05:23,910 like the Explorer for Windows, and I decide to run malware 152 152 00:05:23,910 --> 00:05:25,500 and make you think I'm running it 153 153 00:05:25,500 --> 00:05:27,300 as the Explorer for Windows, 154 154 00:05:27,300 --> 00:05:30,720 I can hide that malware by injecting the code into that. 155 155 00:05:30,720 --> 00:05:32,880 That's the idea of code injection. 156 156 00:05:32,880 --> 00:05:35,100 Now, there's a lot of other techniques we can do 157 157 00:05:35,100 --> 00:05:37,290 as far as different types of code injection. 158 158 00:05:37,290 --> 00:05:39,870 This includes things like masquerading where your dropper 159 159 00:05:39,870 --> 00:05:43,140 is going to replace a genuine executable with a malicious one. 160 160 00:05:43,140 --> 00:05:44,790 You can use DLL injection, 161 161 00:05:44,790 --> 00:05:47,010 where the dropper starts forcing a process to load 162 162 00:05:47,010 --> 00:05:48,510 as part of the DLL. 163 163 00:05:48,510 --> 00:05:50,010 So it's going to load the DLL 164 164 00:05:50,010 --> 00:05:52,380 and the executable malicious code. 165 165 00:05:52,380 --> 00:05:54,420 You also can do DLL sideloading. 166 166 00:05:54,420 --> 00:05:56,790 This is where the dropper is going to exploit a vulnerability 167 167 00:05:56,790 --> 00:05:58,650 in a legitimate program to manifest 168 168 00:05:58,650 --> 00:06:01,050 to load a malicious DLL at runtime. 169 169 00:06:01,050 --> 00:06:02,580 And essentially, use sideload 170 170 00:06:02,580 --> 00:06:04,800 by making it load this malicious thing. 171 171 00:06:04,800 --> 00:06:06,930 Or we can do process hollowing. 172 172 00:06:06,930 --> 00:06:08,670 This is when a dropper starts a process 173 173 00:06:08,670 --> 00:06:09,990 in a suspended state, 174 174 00:06:09,990 --> 00:06:12,060 and then rewrites the memory locations containing 175 175 00:06:12,060 --> 00:06:14,670 the process code with the malware code. 176 176 00:06:14,670 --> 00:06:17,520 So essentially, we're taking over someplace in memory 177 177 00:06:17,520 --> 00:06:19,680 and putting our malicious code in there. 178 178 00:06:19,680 --> 00:06:21,480 Now droppers are likely to implement 179 179 00:06:21,480 --> 00:06:23,310 a lot of these different techniques. 180 180 00:06:23,310 --> 00:06:24,143 In addition to that, 181 181 00:06:24,143 --> 00:06:26,580 they also use some anti-forensic techniques 182 182 00:06:26,580 --> 00:06:28,920 to help prevent detection and analysis. 183 183 00:06:28,920 --> 00:06:30,990 When we talk about anti-forensic techniques, 184 184 00:06:30,990 --> 00:06:33,330 this is things like encrypting their payloads, 185 185 00:06:33,330 --> 00:06:36,810 or compressing their payloads or obfuscating their payloads. 186 186 00:06:36,810 --> 00:06:37,920 Now, when they do this, 187 187 00:06:37,920 --> 00:06:41,250 it makes our job as reverse engineers a lot harder, 188 188 00:06:41,250 --> 00:06:44,070 but we still find ways to find these people. 189 189 00:06:44,070 --> 00:06:46,620 And so one of the things that a lot of pen testers 190 190 00:06:46,620 --> 00:06:48,810 and a lot of attackers are starting to do now 191 191 00:06:48,810 --> 00:06:51,270 is a concept called living off the land. 192 192 00:06:51,270 --> 00:06:53,040 Because when they live off the land, 193 193 00:06:53,040 --> 00:06:55,050 it's really hard for us to find them. 194 194 00:06:55,050 --> 00:06:56,490 When I talk about living off the land, 195 195 00:06:56,490 --> 00:06:59,370 this is an exploit technique that uses standard system tools 196 196 00:06:59,370 --> 00:07:01,830 and packages to perform their intrusions. 197 197 00:07:01,830 --> 00:07:03,750 For instance, they might use something like this, 198 198 00:07:03,750 --> 00:07:05,190 which is PowerShell. 199 199 00:07:05,190 --> 00:07:06,390 PowerShell can be used to do 200 200 00:07:06,390 --> 00:07:08,550 all sorts of malicious activities. 201 201 00:07:08,550 --> 00:07:10,920 And so what we can do is when we break into a system 202 202 00:07:10,920 --> 00:07:12,870 as a pen tester or as an attacker, 203 203 00:07:12,870 --> 00:07:15,510 we can actually use your own PowerShell against you. 204 204 00:07:15,510 --> 00:07:17,820 If I'm on a Linux system, I can't use PowerShell, 205 205 00:07:17,820 --> 00:07:19,380 but I can use Bash scripting. 206 206 00:07:19,380 --> 00:07:21,330 And so again, if I use the tools that are native 207 207 00:07:21,330 --> 00:07:22,920 to your operating system, 208 208 00:07:22,920 --> 00:07:24,990 I am now using tools that were already installed 209 209 00:07:24,990 --> 00:07:26,040 for your administrators, 210 210 00:07:26,040 --> 00:07:27,720 and I'm using them in a malicious way, 211 211 00:07:27,720 --> 00:07:29,700 but it's going to be really hard for you to detect that 212 212 00:07:29,700 --> 00:07:31,470 because I'm living off the land. 213 213 00:07:31,470 --> 00:07:33,630 So if you fall victim to an attacker who is used 214 214 00:07:33,630 --> 00:07:34,680 to living off the land, 215 215 00:07:34,680 --> 00:07:36,000 the detection of that adversary 216 216 00:07:36,000 --> 00:07:37,710 is going to be much more difficult 217 217 00:07:37,710 --> 00:07:39,270 because they're executing malware code 218 218 00:07:39,270 --> 00:07:41,670 within those standard tools and processes, 219 219 00:07:41,670 --> 00:07:43,740 and that makes it really hard to detect, 220 220 00:07:43,740 --> 00:07:44,940 and it's going to allow them to stay 221 221 00:07:44,940 --> 00:07:46,503 on your system a lot longer.