Operation DarkCasino: In-Depth Analysis of Attacks by APT Group Evilnum (Part 2) - NSFOCUS, Inc., a global network and cyber security leader, protects enterprises and carriers from advanced cyber attacks. By NSFOCUS Published: 2022-09-20 · Archived: 2026-04-05 16:29:06 UTC Operation DarkCasino: In-Depth Analysis of Attacks by APT Group Evilnum (Part 1) Components Evilnum mainly used a new customized trojan in this operation. NSFOCUS Security Labs named it DarkMe based on the particular string in the trojan program. NSFOCUS Security Labs also discovered another new trojan program that had a close connection to this operation and named it PikoloRAT, also based on the particular string in the program. 1. DarkMe DarkMe is a VisualBasic spy trojan developed by Evilnum attackers and is used in various attack flows. The initial version of DarkMe appeared on September 25, 2021, and five iteration versions have been released so far. The communication ability of DarkMe is implemented through the public module WinSock32 (http://leandroascierto.com/blog/winsock32/). This module creates a window named SOCKET_WINDOW to implement socket communication with the server. On the basis of this module, a significant number of functional codes are gradually added to DarkMe, allowing it to evolve from a downloader trojan into a stub spy trojan. Functions Different versions of DarkMe have different functional codes. Here, we will describe the trojan program version 5, ShellRunDllVb.dll, that appeared in this operation. After ShellRunDllVb.dll is executed, it will collect host information and send it to the C&C server. DarkMe collects the following host information, including the geolocation abbreviation, country name, computer name, user name, antivirus software list, trojan mark, and the title of the foreground window. These items are separated by a fixed separator 0x3F, and prepended with a fixed string “92”. The resulting register information is then sent to the C&C server. https://nsfocusglobal.com/operation-darkcasino-in-depth-analysis-of-attacks-by-apt-group-evilnum-part-2/ Page 1 of 11 Register traffic of DarkMe DarkMe has multiple modules to support different espionage functions. clsfile is a major module used to implement file operations under C&C control. The C&C instruction is contained in the first six bytes of the communication content. The function of each instruction is described as follows: Description of DarkMe instructions In addition, DarkMe has been integrated with a set of public codes to achieve the screenshot function. Screenshot function implemented by DarkMe (right) and public code (left) DarkMe also provides persistence and self-updating functions as well as the keylogging function in some versions. Versions With a deeper look at samples in the wild, NSFOCUS Security Labs found DarkMe had a history of more than half a year, and was already available in multiple versions. The version iteration timeline of DarkMe is as follows: https://nsfocusglobal.com/operation-darkcasino-in-depth-analysis-of-attacks-by-apt-group-evilnum-part-2/ Page 2 of 11 Version iteration of DarkMe It can be seen that during its lifecycle, DarkMe has evolved from a loader trojan to a spy trojan, and then to a stub payload integrated into complex attack flows. DarkMe version 4 and DarkMe version 5 both have complete code functions and can be used as a primary stealing tool or as a loader for other tools, so they were widely adopted by Evilnum attackers in recent attacks. 2. PikoloRAT NSFOCUS discovered another new remote control trojan, PikoloRAT, during the in-depth analysis of the relevant information of this operation. PikoloRAT comes with typical remote control functions and can use built-in components to implement more complex control operations. Since the built-in C&C addresses of PikoloRAT were found to coincide with the addresses used in this operation and PikoloRAT could complement the above-mentioned DarkMe, NSFOCUS Security Labs believed that PikoloRAT was used as an extension component by Evilnum attackers in the later stage of this operation. The discovered cases demonstrated that PikoloRAT was delivered via a downloader trojan or packaged as a compressed file. Functions PikoloRAT is a typical RAT trojan program written in C#. Main frame of PikoloRAT After PikoloRAT runs, it first collects and uploads the host information. The collected contents include the trojan mark, user name, computer name, geolocation, operating system version, trojan running time, trojan version, and antivirus software information. PikoloRAT uses a “|” to separate the preceding items, prepends them with a fixed string “654321”, and then sends it to the C&C server. https://nsfocusglobal.com/operation-darkcasino-in-depth-analysis-of-attacks-by-apt-group-evilnum-part-2/ Page 3 of 11 Online traffic of PikoloRAT It can be seen that the content and format of the online traffic of PikoloRAT are similar to those of the above-mentioned DarkMe. Then PikoloRAT enters the controlled state to control host behaviors by obtaining instructions from C&C servers. The supported remote control instructions are as follows: Description of PikoloRAT instructions In addition to basic remote control functions, PikoloRAT can perform more sophisticated remote control by dropping the built-in PEGASUS HVNC module, a recently leaked hVNC tool. Techniques and Tactics https://nsfocusglobal.com/operation-darkcasino-in-depth-analysis-of-attacks-by-apt-group-evilnum-part-2/ Page 4 of 11 Overwriting Files While Sideloading In attack flow A, Evilnum attackers delivered a malicious file python39.dll and sideloaded it through a legitimate file python.exe. Different from common sideloading build logics, python39.dll was obtained by directly overwriting the original python39.dll. Evilnum attackers directly wrote a piece of shellcode to the location of the function PyImport_AddModuleObject of the original python39.dll so that the shellcode was started when python39.dll was loaded. The benefits of this design are: Easy to operate. It is not required to compile a separate DLL program to implement the export. Wide applicability. In theory, any legitimate DLL file can be overwritten in a similar way to build a sideloading shellcode attack chain. Strong concealment. The new DLL file is so similar to the original DLL file that it is not easy to locate. Overwritten PyImport_AddModuleObject function in python39.dll Shellcode Framework In attack flow A, Evilnum attackers used different shellcodes at different stages. Since these shellcodes had similar code implementation logic, NSFOCUS Security Labs believed that they originated from the same shellcode programming framework. The overall composition and code complexity in this operation were improved compared to previous Evilnum activities. ntdll Mapping In the shellcode used in this operation, Evilnum attackers still adopted two modules, kernel32 and ntdll, to build the main attack flow. To avoid API detection for such behaviors, the attackers used the following method to map the ntdll file and use the API of the mapped file. Mapping logic of the ntdll module in the shellcode In the implementation, the attacker reloaded the ntdll module through file mapping, and obtained the API base address of the mapped API by calculating the offset of the base address of the API in the original ntdll file. Then the shellcode used the mapped API to implement corresponding behaviors, thus avoiding original API call behaviors and preventing key parameters from being monitored and recorded. X64call In attack flow A, Evilnum attackers used X64call to call key APIs while injecting cmd.exe. https://nsfocusglobal.com/operation-darkcasino-in-depth-analysis-of-attacks-by-apt-group-evilnum-part-2/ Page 5 of 11 The injected shellcode firstly detected the process environment and the host CPU model. If the requirements were satisfied, it would call their 64-bit implementations while using key injection APIs such as NtAllocateVirtualMemory and NtWriteVirtualMemory. X64call calling logic in the shellcode injection code X64call calling code This technique can also bypass API detection. Image Steganography Evilnum attackers used two types of steganographic images in this operation. In attack flow B, the image IMG.jpg used redundant steganography that deposited the malicious code at the end of the file and used a fixed string ($HEH$E) as the separator. Steganographic information in IMG.jpg. In attack flow A, the image carrying the payload used the RGB color image steganography scheme that deposited the malicious code in the R color pixel. RGB values in the steganographic image sKr93I.png (right) and extracted compressed data content (left) This construction could make blue-green dots show in white areas and red dots show in black areas in the steganographic image. https://nsfocusglobal.com/operation-darkcasino-in-depth-analysis-of-attacks-by-apt-group-evilnum-part-2/ Page 6 of 11 Appearance of the steganographic image sKr93I.png Appearance of the steganographic image Fruit.png Socket Window In this operation, the trojan DarkMe used SOCKET_WINDOW communication, an old VisualBasic socket programming technique that hooks winsock messages through a SOCKET_WINDOW window and handles event messages passed by WSAAsyncSelect in the window callback function. For the original framework, refer to here. COM Component Execution Some DarkMe trojans were delivered as COM components in this operation. Evilnum attackers wrote the registry operation logic to the preloaded trojan payload, allowing it to generate and execute the file Register.reg that contained the following contents. Contents of Register.reg Then the preloaded trojan payload started DarkMe via a cmd command in the form like rundll /sta [CLSID] ‘Hello’. This could avoid direct calls to DarkMe, reducing exposure risks to a certain extent. Conclusion https://nsfocusglobal.com/operation-darkcasino-in-depth-analysis-of-attacks-by-apt-group-evilnum-part-2/ Page 7 of 11 Operation DarkCasino is a series of ongoing APT attacks targeting cash flows in online trading. The Evilnum group adopted a variety of ever-improving attack techniques and tools, demonstrating its keen sense of confrontation. The analysis showed that the attack scope of Operation DarkCasino was not limited to Europe. Under the operation of the Evilnum attackers, this attack was extended to some Asian countries, which may cause unexpected damage. To effectively prevent this operation, online financial platform users should pay special attention to files of LNK, PIF, SCR, and COM types transmitted through various channels and be more vigilant of files with keywords such as offer, visa, and casino to avoid Evilnum attacks, which may cause direct economic losses. Indicators of Compromise (IoCs) Decoy files of attack flow A 43eda4ff53eef4513716a5b773e6798653ee29544b44a9ae16aa7af160a996f2 offer deal visa 2022.lnk Decoy files of attack flow B 5fb252474237a4ca96cc0433451c7d7a847732305d95ceeaeb10693ecef2eeee Scatters Casino offers Daily Promotions.pif 8e4a4c5e04ff7ebacb5fe8ff6b27129c13e91a1acc829dbb3001110c84dc8633 new casino crypto.com d0899cb4b94e66cb8623e823887d87aa7561db0e9cf4028ae3f46a7b599692b9 Promo CPL CPA Traffic.com Decoy files of attack flow C 4ffa29dead7f6f7752f2f3b0a83f936f270826d2711a599233dc97e442dee85f 333TER.exe 9cf7f8a93c409dd61d019ca92d8bc43cc9949e244c9080feba5bfc7aac673ac3 d33v3TER.exe 259cebed2cd89da395df2a3588fadde82cd6542bc9ff456890f7ee2087dc43c9 d333TER.exe 0cdf27bb8c0c90fc1d60fb07bd30b7e97b16d15e3f58fb985350091ecad51ba6 ed333TER.exe 5ba84191a873d823ccf336adfa219cc191a004e22b56b99c6d0e1642144129b8 wed333TER.exe 15a076c7bb6a38425d96aa08b8a15e9a838c9697d57c835aaca92fd01607b07a PayRedeemUpdateIntegration19052022.scr 3329f5e3a67d13bd602dca5bbe8e2d0b5d3b5cb7cb308965fb2599a66668c207 offer crypto casino.scr 8a49a7f6c95fade72ef86455794cdedfca9129aa0f5281e09929dfebfb3417c4 DOCUMENTATION AGREEMENTS S CONSULTING INTEGRATION.pif Downloader Trojan 864dccbeda7d88cad91336b5ae9efd50972508d1d8044226e798d039a0bc1da2 AONNRJP.exe PikoloRAT Trojan eb5e42c726c7b125564455d56a02b9d42672ca061575ff911672b9165e8e309d stub1.exe https://nsfocusglobal.com/operation-darkcasino-in-depth-analysis-of-attacks-by-apt-group-evilnum-part-2/ Page 8 of 11 be544a1f9f642bb35a9bd0942ae16a7a6e58a323d298a408a00fa4c948e8ea17 Stub1.exe DarkMe Trojan a826570f878def28b027f6e6b2fcd8be1727e82666f8b65175d917144f5d0569 Project1.exe 7b478cd8b854c9046f45f32616e1b0cbdc9436fa078ceddb13ce9891b24b30a5 Project1.exe e72337c08d6b884b64fd9945c5a01557ccf40db93af866c00c48d36b6605f3a0 Project1.exe 414a11e8eabb64add97a866502edcd7e54108bd247f4ae12fe07feeae4e549f6 Projec3.exe 7913cdf40cc17a28487a71ab0d7724b8bf3646a2a53e3905798ce23a657061b8 Project1.exe 3a6694567e9d722357b8e92153d9c878bbcab55a2f65cd0f9a2e6579fbeb935a Projec3.exe a6a70c85b8c40932678c413fde202a55fcfc9d9cae23822708be5f28f9d5b6d2 Projec3.exe c50ebe13972e6e378248d80d53478d8e01e754c5d87113d9b6f93bf3b84380b4 Project1.exe 1ac7715b1762788b5dc1f5f2fc35243a072fe77053df46101ce05413cca62666 Projec3.exe 4ecc2925cfb073323314611a3892d476a58ff2f6b510b434996686e2f0ac3af7 Projec3.exe 541b3011953a3ce1a3a4a22c8c4f58c6a01df786a7cc10858649f8f70ee0a2f3 Projec3.exe f25cbc53d0cc14b715ee83e51946d5793e4e86e71e96f68e9b6c839b514e8cb8 Projec3.exe 4244f274a12f4672f2dda1190559d96c5a9631c9ee573b853c89e30701819b63 Projec24.pif 1f0d908c677fb3ec5b9422eb5f7d2a2b3ffa01659521afc07cc4dfaea27aa532 Nuovo.pif 028057e54a2e813787a14b7d33e6a2caa91485ed879ef1bbcb94df0e1cf91356 bvo.exe 0a9c183f0b5a225228da5e8589fac8b3affe2e51c790a08148ef72481de610c4 bvo.exe 3eb84676249cb26dd3d1962cfca2a9fde442d0feaa1b0351f6331313f3ac1138 bvo.exe 46fbfc263959084d03bd72c5b6ee643711f79f7d76b391d4a81f95b2d111b44e bvofinal.pif 5e04dd49b82320eca63b483e87453d2a68a9f4873f47d37e5080d537bc811d0e pppppesst.exe dc8190279dcea4f9a36208ba48b14e6c8313ef061252027ef8110b2d0bd84640 pppppesst.exe 4959cdba7edee68b5116cc1b8ef5016978d3dff2016f027a4f76b080b7c3849a faster.exe 24ace8fd73b2a5a13f3e5b459f0764dd4b5bda2cea2b0e13bbf88a88afe0cdac fastest.exe c66e6ee55e9799a8a32b7a2c836c26bb7ebea98d09c1535ad9ae59e9628835fb fastest.exe 32ce8d0dcbfcc2517480d0e08f8896ab4f6ea13ccb0eefe7205cd352c7b359c3 h5a.exe c192684d296ea587e93457d060cbef900143cf1a11301e6c2e34e264e3e55ef6 h5a.exe 1d01b143a56eba431387b9b973790d174deb48c2e3445d96b131a7d8e0a9d4ef vvt1.exe b8ba2c0478649dc099d0a869755a7e205173a9b0d15fad920317a89d07eaa930 vvt1.exe https://nsfocusglobal.com/operation-darkcasino-in-depth-analysis-of-attacks-by-apt-group-evilnum-part-2/ Page 9 of 11 d95853e6e16d90c00fd72aaeaca9885b953dae14d7d6aa7fedcc6150fb788667 656.exe 7add6700c6e1aa1ac8782fdd26a11283d513302c672e3d62f787572d8ad97a21 ShellRunDllVb.dll 17fe047b9a3695d4fd8ad9d2f7f37486c0bc85db0f9770471442d31410ff26a1 ShellRunDllVb.dll 2665a09ec5b4ca913f9f3185df62495f13611831dba9073779a36df088db143b ShellRunDllVb.dll 7c06a03d712be8c0df410bea5d1c2004c6247bcde5a46ce51746f18de9621ac1 ShellRunDllVb.dll URL https[:]//puccino.altervista.org/wp-content/uploads/2022/05/6h.txt https[:]//storangefilecloud.vip/IMG.jpg https[:]//storangefilecloud.vip/PI.txt https[:]//storangefilecloud.vip/PRGx.jpg https[:]//bukjut11.com/FRIGO.JPG https[:]//bukjut11.com:443/AEVC.JPG https[:]//imagizer.imageshack.com/img922/1527/sKr93I.png https[:]//imagizer.imageshack.com/img923/7651/jMwIGI.png https[:]//i.imgur.com/fkNiY9Z.png https[:]//laurentprotector.com/LRGBPFV.bin https[:]//laurentprotector.com/NnQFqsOEUtkezvIEcLpfa.bin Darkme C&C aka7newmalp23.com csmmmsp099q.com muasaashishaj.com cspapop110.com 938jss.com 8as1s2.com kalpoipolpmi.net pallomnareraebrazo.com 185.236.231.74 PikoloRAT C&C 51.195.57.232 https://nsfocusglobal.com/operation-darkcasino-in-depth-analysis-of-attacks-by-apt-group-evilnum-part-2/ Page 10 of 11 Source: https://nsfocusglobal.com/operation-darkcasino-in-depth-analysis-of-attacks-by-apt-group-evilnum-part-2/ https://nsfocusglobal.com/operation-darkcasino-in-depth-analysis-of-attacks-by-apt-group-evilnum-part-2/ Page 11 of 11