al.. (2018, December 18). How can you use this malware to get user credentials from your test environment? Han, Karsten. Generally after cmp, jumps if destination operand != source operand), jg loc (Jump if Greater. Next create a COM serial port that uses a named pipe which our debugger will communicate with. If we wanted to limit this to one hardcoded element over another it would be trivial to do; however for the purpose of thoroughly identifying every static element of this beacon for a high confidence hit, we have added all to our Snort rule. Cross-references in red may indicate anti-disassembly is being used. This is what is used for running a single assembly instruction. Function calls the ret instruction which pops return address off stack and onto EIP. Lee, B, et al. When bundled with rep, this is equivalent to memset in C. Malware is often written in C. A C program often has 2 arguments for the main method with argc and argv. This is also seen at 0x402020 in OllyDbg. One way to reduce the number of irrelevant entries is to add a filter that only shows operations that contain the words ‘set’ or ‘create’. Will have multiple compare and jump statements close to one another, and any ‘false’ result leads the next compare to happen. Retrieved July 9, 2018. Uses size of disassembled instruction to determine next byte to disassemble. Based on results of Ida-Ent, KANAL, and by looking at this in IDA, we can begin to assume that the algorithm used for encoding is custom, and not something easily fingerprintable. After this further checks and calculations occur to determine what special key is being pushed, and in the event one is a specific value is outputted to the keylog file. To get this we will focus on the ‘s’ character followed by any number of numbers between 0 and 20 characters long, closed by our signature 96’. Another variant decodes the embedded file by XORing it with the value "0x35". What happens if the string comparison to robotwork is successful (when memcmp returns 0)? If we wanted to go a step further we could then use this to hunt for hits across a public malware repository such as Hybrid Analysis which is powered by MalQuery. You can run the executable from anywhere, but in order for the program to work properly, the driver must be placed in the C:\Windows\System32 directory where it was originally found on the victim computer. Sierra, E., Iglesias, G.. (2018, April 24). As such if we examine cross-references to ‘sub_401082’ we find it is called inside a windows API call to ‘StartAddress’ used to start its own thread, which if we once again examine cross-references find it is called within ‘sub_4015B7’. By examining the program’s execution after creating a service for persistence, we can see that it sets up a timer checking for when the year is 2100 (834h), or midnight on January 1st 2100. The SAML token contains different timestamps, including the time it was issued and the last time it was used. Jumps if the Sign Flag is set), jecxz loc (Jump if not ECX. (2015, June 23). This conclusion is drawn as ‘GINA” stands for ‘graphical identification and authentication’ which is a component of these older operating systems. The below outline basic arithmetic operations and ways of remembering them within assembly. By running ‘g’ the application runs and hits our new breakpoint. Retrieved May 26, 2020. This can also remove function argument names which would otherwise be present. What is the base address requested by DLL1.dll, DLL2.dll, and DLL3.dll? If you look carefully you can see that although we only had rules created for binaries in Lab01, we’ve successfully identified binaries with similar attributes at the below: The results proved we didn’t mess anything up and the Yara rules worked. What rogue opcode is the disassembly tricked into disassembling? After graphing user defined xrefs, we can see the relation between these 2 functions. Methods for doing that include built-in functionality of malware or by using utilities present on the system. Once again, trying a different tool to keep things fresh, PE Detective revealed that this file was packed this time using FSG. Retrieved January 11, 2021. Following this we can see that the output of sub_10003695 will be moved directly into dword_1008E5C4. If we run strings over Lab11-03.dll we can once again see a number of strings of interest. What command-line argument will cause the program to print “Good Job!”? Relevant opcodes of interest include E9 (5-byte jmp) and E8 (5-byte call). Use IDA Pro to look for potential encoding by searching for the string xor. First we need to determine where the breakpoint in our VM will be that calls the ControlService function. In this we can quickly see reference to a key being provided. 3 key calls we find are CreateFile, CreateFileMapping, and MapViewOfFile. Note: This is registered in milliseconds so the value passed is multiplied by 1000. [14], Bankshot decodes embedded XOR strings. Special thanks to No Starch Press for the shout-out of this post, and to both Michael Sikorski and Andrew Honig for their permission to create this blog post based on the material and exercises contained within ‘Practical Malware Analysis’. In Lab 6-3 the calls directly from the main method consist of: In Lab 6-4 the calls directly from the main method consist of: What new code construct has been added to main? To get the third part of our detection pattern we can simply match on 4 or more characters. In the below example we’ve used explicitly python 3.6 to avoid some bugs present in python 3.5. If we look at the Strings window of this malware we can see what appears to be a Base64-encoding index string. Of interest is that this has a modified ‘padding’ character used as ‘61h’ (a) meaning that any padding required in the Base64-encoded data will appear as the letter ‘a’ rather than the standard ‘=’. Note: This isn’t a typo, in this instance download is in fact uploading to a remote the host. Move ExistingFileName to NewFileName and call the subroutine ‘sub_4011FC’. OPERATION GHOST. Based on question 1, it’s likely that the imported function ‘WriteFile’ would be a good prospect for finding the encoding functions given the data we found inside of the written files looks to be encoded. Signed jump after cmp, jumps if destination operand is < source operand), jle loc (Jump if Less or Equal. Initially the program will check if a keylog file is present, and if it isn’t it’ll look to first create it. New KONNI Malware attacking Eurasia and Southeast Asia. (2017). Based on this we can assume that the URL and GET request resource this reaches out to is encoded. By running this program and examining it with Procmon we can see that it creates a kernel driver and writes it to disk. Looking at the cross-references we can see that they’re all within the sub-routine ‘sub_401000’, so we’ll take a look at this closer to see if we can find any obvious constructs. ESET. Looking at the exports of ‘Lab11-03.dll’ which we know is copied to this location, we can see this is a valid export. What’s apparent is that outgoing connections use a hardcoded User-Agent which can be used to fingerprint this malware. Based on this we can infer that if an executable file is located, it is is mapped into memory and can then be modified by this program. (2015, August 10). Adamitis, D. et al. Continuing on we can see entries such as: idle, uptime, mmodule, minstall, and inject all catch out eyes. Once we reach the main function, if we press F8 the program runs through it which isn’t what we want. Based on the response received, we can begin to assume that the response to commands run from the C2 of this malware is encoded. (2020, December 13). Tedesco, B. 0x90, does nothing and goes to next instruction. No, there’s no indicators these files are packed or obfuscated due to the following: Using PEiD we can identify them as being compiled with Microsoft Visual C++ 6.0. Examining the calls in Lab6-2 and Lab6-3 show a number of similarities; however, 1 subroutine exists in Lab6-3 which is new and is called “sub_40113”. Hancitor (AKA Chanitor) observed using multiple attack approaches. [74], PlugX decompresses and decrypts itself using the Microsoft API call RtlDecompressBuffer. By using CFF Explorer VIII we can see that msgina32.dll exports a number of functions that correlate to known functions that need to be exported by a legitimate GINA DLL as it is prepended with Wlx. Assigning variables (int a = 0; int b = 1;): Must be a conditional jump (e.g. So long as the registry is successfully opened, the answer would be “False”, “No”, or in terms of the Zero-Flag “0”. This is a common string obfuscation technique to make analysis more challenging. DOWNLOAD: Upload a file from disk to a web resource. Retrieved July 16, 2018. The closer to 0, the less random (uniform) the data is. Malwarebytes Labs. This looks similar to a for loop, except without incrementation. What advantages does this source offer? Given we’ve already defined ‘CYBERAIJU’ to point to one of our controlled hosts, let’s continue to use this, and create a Snort rule based on all the hardcoded elements of this beacon. Using PE-bear we are able to easily see the exports of this DLL file. Due to the malware infecting every executable on disk it is very difficult to remove. A token having the same timestamp for when it was issued and when it was used is not indicative of normal user behavior as users tend to use the token within a few seconds but not at the exact same time of issuance. By repeating this process we find the following six functions perform xor operations that look like they may be encoding, of which the type of encoding is not yet clear. Counter Threat Unit Research Team. Working our way back to sub_401070 which we discovered before the encoding function took place, we can see that in addition to calling GetDesktopWindow to get a handle to the current screen, there’s calls to BitBlt and GetDIBits which is associated with getting pixel colour and layout of the desktop, which helps us to infer this is taking a screenshot. Lazarus Continues Heists, Mounts Attacks on Financial Organizations in Latin America. Retrieved November 26, 2018. [114], One TYPEFRAME variant decrypts an archive using an RC4 key, then decompresses and installs the decrypted malicious DLL module. If we then run the same search and look for the first xor operation that falls after 00402237 (004022DD), we find another subroutine (sub_40223A) which begins at 0040223A and ends at 004027EA, so we give it a name of XOR_OP_1. This also uses a call to ‘sub_401147’ so we know the argument passed takes uses the previously identified decoding routine. It adds a hotkey to allow converting an instruction to a ‘NOP’ at the current cursor location. The first is that it issues a CreateFile API call to the below: Because we know that the CreateFile can be used for either creating or reading a file, we can look a little bit deeper at the properties of this event. Retrieved September 23, 2020. [5], An APT19 HTTP malware variant decrypts strings using single-byte XOR keys. Once this program is running, how do you stop it? [44], Honeybee drops a Word file containing a Base64-encoded file in it that is read, decoded, and dropped to the disk by the macro. Using the Krypto ANALyzer (KANAL) plugin for PEiD, we can find Base64 encoding being used at ‘0x004050E8’. What is the significance of the .ini file? Will continue until ECX = 0 or buffers aren’t equal. Because this will be run by winlogon.exe we can expect this to fall within the directory C:\Windows\System32. To determine the source of this IP we can work back from the networking calls we found inside of WinInet.dll using IDA. Function prologue creates space on stack for local variables, and EBP. Based on the GetWindowsDirectory function we can assume this will write files to the system directory, and will then execute them due to the WinExec function. Retrieved December 20, 2017. By looking at when this subroutine finishes we find that it finishes at ‘00402237’. Retrieved August 7, 2018. What host- or network-based indicators could be used to identify this malware on infected machines? In the same area, at 0x100101C8, it looks like dword_1008E5C4 is a global variable that helps decide which path to take. We need to install Yara if we haven’t already. (2017, December 7). What happens when you run the malware executable? Yan, T., et al. Upload the Lab01-02.exe file to http://www.VirusTotal.com/. It’s possible you may receive an error message around verifying checksums, but attempting to run the breakpoint again ensures it is set. If we examine using Resource Hacker, we can see this is instead called ‘LOCALIZATION’. The combination of these alerts is enough for any responder to have a strong indication of malicious activity occuring on this system. In this case we find that it is called within ‘sub_40132B’ which is started in a thread after cmd.exe has been run and our previous StartAddress call has run. This is because when we’re talking about Zero Flags, we’re essentially asking “Is this false?”, and if it is true (1=True), the Zero Flag IS NOT set, if it is false (0=False) then the Zero Flag IS set. If not, it will create a Mutex with this name. Here we can see evidence of information being written to this file before a timeout of ‘0A’ (10) milliseconds occur and it repeats. Safest option is to not be connected to the internet when analysing malware. A comparison between WinInet and WinHTTP can be found here. Jump with constant condition: Common anti-disassembly technique and is made up of a single conditional jump where the condition is always the same. The offset 0x666 on the other hand is calling IoGetCurrentProcess which we identified earlier, before accessing data at 0x88, and 0x8C (0x88 + 4). Lancaster, T., Cortes, J. ECX = Buffer length. [76], PUNCHBUGGY has used PowerShell to decode base64-encoded assembly. Based on our Findcrypt results in Ghidra, we know that anything labeled Td0 to Td3 is related to a decryption AES operation, and anything labeled Te0 to Te3 are related to an encryption AES operation. Trustwave SpiderLabs. Note: When attempting to run yarGen.py I experienced an issue with ‘etree’ being imported from lxml. In this instance there’s also the usage of ‘%c’ to help backup this inference. [75], PolyglotDuke can use a custom algorithm to decrypt strings used by the malware. Examining the calling process reveals this would wait ‘0EA60h’ (60000) milliseconds if this fails and try to download it again. Retrieved August 4, 2020. Based on this comparison, which elements might be encoded? (2019, July). [84][85][86][87][88][89], RGDoor decodes Base64 strings and decrypts strings using a custom XOR algorithm. Linked List is data structure with data records which contain a reference (link) to the next record in the sequence. Retrieved November 5, 2018. Retrieved May 19, 2020. What else must be known? Alintanahin, K. (2015). New targeted attack against Saudi Arabia Government. Impossible disassembly: Occurs when a ‘rogue byte’ e.g. From the imports of Lab12-01.exe we can begin to assume it may perform some type of process injection due to the API calls involving multiple of the below which are commonly used for process injection. Upload the Lab01-04.exe file to http://www.VirusTotal.com/. [37], Gamaredon Group tools decrypted additional payloads from the C2. This is useful for user mode debugging on single compiled binaries. Drilling into this we first look at the cross references to ‘sub_401070’ which is called prior to starting ‘cisvc’. (2018, November). By using G to go to the address of interest (in this case sub_10004E79), we can then click View > Graphs > XRefs From to see a number of API functions within this function. If the character sent is 15 higher than ‘d’ the switch case to run is 3. Upon hitting 0x402AFD we can see a comparison takes place to see if the number of arguments passed to the program is equal to one. (2018, June 26). To test any Snort created rules we will need to simulate a command being sent from the initial beacon. Lee, B., Falcone, R. (2018, June 06). Thomas Reed. From this we can see that installer doesn’t seem to perform many more calls than what we’ve already identified. This is a decoding routine that’s elaborated further in Question 4. 0x42), General registers used by the CPU at execution, Segment registers used to track sections of memory, Instruction pointers used for process flow, EAX contains the value 0xA9DC81F5 (32bits). Retrieved April 17, 2019. To figure this out we need to move into the encoding routine at 0x00401089. The following network trace is of one of the most relevant POST action taking back pattern with many “/” In addition this gets Generic Read/Write access to C:\WINDOWS\sytem32\cisvc.exe, but doesn’t perform any type of file write operations. Carbon Black Threat Analysis Unit. Updated BackConfig Malware Targeting Government and Military Organizations in South Asia. EDX or ECX). Which API functions could be called by entering this function? If we follow the previous routine at offset 10019020 (off_10019020), we see it points to the data reference unk_100192AC. By repeating the process once more we see that it fails to run through to our later break points in our isolated environment. [16], Bisonal decodes strings in the malware using XOR and RC4. What type of encoding is used for command arguments? Counter Threat Unit Research Team. After resuming the malware again, if we allow it to complete a new file will be created. Villanueva, M., Co, M. (2018, June 14). We now know that this process acts as the reverse shell allowing access to this host. In addition we expand our procmon search to include any process with the name cisvc.exe, given this seems to be accessed so may hold more information. By examining sub_401070 which is called by the above function, we find this may be performing some type of screenshot involving an open window based on its imported APIs. To determine the AES encryption key we go back to the earliest known address which appeared to be associated with encryption, and in this case it’s address 00401AC2 under XOR_OP_1 as we identified it looking for XOR operations. Using the Malcode Analyst Pack we are able to perform this by simply right clicking the files and selecting VirusTotal. Based on the imports from Kernel32 we can see that this will load resources from the file’s resource section and write files to disk. [47][48], ISMInjector uses the certutil command to decode a payload file. Looking at the only calling function to this, we can see that the argument passed to this is the established socket to the C2. Once again we can see this is checking whether the operating system is Windows NT or later; however, even if it is, it is then checking if it’s major version is 5. If we take a look at the AES decryption routines built into CyberChef, we can see that based on the AES standard implemented you will also likely need to know the key size and algorithm, any Initialisation Vector, and the mode used to encrypt the content. [33], OopsIE concatenates then decompresses multiple resources to load an embedded .Net Framework assembly. By examining sub_401613 (s) we can see that this looks to be a simple sleep function which sleeps for 20,000 milliseconds if no argument was given, otherwise it sleeps for however many seconds were sent as an argument. It’s recommended a backup of the malware be created. Forum zur Ukraine: Diskussionen, Tipps und Infos zu Reisen, Sprachen, Menschen, Visa, Kultur oder für nette Bekanntschaften in der Ukraine Falcone, R., Lee, B. If we expand these comparisons out and sort by the position number we get the below: This in turn allows us to see it is checking for the entry “”. [4], Azorult uses an XOR key to decrypt content and uses Base64 to decode the C2 address. Search for usage of the in instruction (opcode 0xED). It performs the AES encryption, and then writes the output back to the console (which in this case is redirecting the output back through the established socket). If this is accessed often will slow down a program from running. To determine if this can be leveraged to decode the content, we can look at this more closely in a debugger such as OllyDbg. This helps us identify that the malware will send the hostname running it Base64-encoded in a GET request to www.practicalmalwareanalysis.com and repeat this approcimately every 30 seconds. From here on our host OS we can setup a fake smtp daemon debugging server to receive emails with the below (substituting the IP as required). x86 (32-bit) programs support hardware registers and hardware breakpoints. If we open up IDA and look for reference to this beacon based on the User-Agent, we find that in addition to the above 3 elemets, the header fields of ‘Accept’ and ‘Accept-Encoding’ are also hard-coded, as is the beacon URL. At this point it’s worth analysing the driver using IDA to gather more information on what has occurred. Within this subroutine we can see references to opening the Service Control Manager (SC Manager) and evidence of a service creation which will be used for persistence. Broadly speaking the process to follow is below: This details analysis undertaken and answers to the lab questions in Chapter 3. This is modified to set the previous linked process to skip over the process that made this call when looking forward. Retrieved June 18, 2019. Based on this we can assume that searching hosts for the scheduled service called ‘malservice’ and looking at any hosts connectiong to ‘http://www.malwareanalysisbook.com’ would serve as reliable host and network indicators. Why might the information embedded in the networking beacon be of interest to the attacker? MITRE ATT&CK and ATT&CK are registered trademarks of The MITRE Corporation. What is the key used for encoding and what content does it encode? Further analysis of the binary in IDA reveals that the main method contains a number of checks and operations, before calling sub_401000 with a relevant processID. ]com is resolved. If we give this new file a .bmp extension, we’re able to view it and see it is a recovered screenshot as expected. Taking a closer look at sub_10006518 we can see based on the API call to CreateToolhelp32Snapshot, strings, and the function name that this will allow them to grab a process listing. CORONAVIRUS vaccine rollout starts in less than 24 hours, marking the beginning of the end of the pandemic. Due to this the total number of bytes that will be copied is 78 * 4 = 312 bytes. Compare the strings in the malware (from the output of the strings command) with the information available via dynamic analysis. [55], menuPass has used certutil in a macro to decode base64-encoded content contained in a dropper document attached to an email.
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