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	"title": "Understanding BumbleBee: The malicious behavior of BumbleBee - VMRay",
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	"plain_text": "Understanding BumbleBee: The malicious behavior of BumbleBee\r\n- VMRay\r\nBy VMRay Labs\r\nPublished: 2023-08-18 · Archived: 2026-04-05 13:00:33 UTC\r\nDownload The Report\r\nIntroduction\r\nHaving meticulously dissected the intricate delivery methods employed by BumbleBee in our previous blog post,\r\nwe embarked on a journey through the multifaceted and complex delivery chains that enable its stealthy\r\npenetration. From the covert utilization of seemingly innocuous files to ingenious tactics that evade detection, we\r\nnavigated through the diverse arsenal BumbleBee wields to gain access.\r\nNow, our exploration of this malicious loader takes us deeper into its heart — its behavior within the targeted\r\nenvironment. As we journey through its maneuvers, we seek to unravel the layers of complexity that lie beneath\r\nits surface. With a focus on unveiling the true essence of BumbleBee’s actions post-infiltration, we uncover the\r\nevolution and adaptation that contribute to its resilience.\r\nBumbleBee Blog Series – 2\r\nDOWNLOAD THE E-BOOK\r\nUnpacking Executables\r\nMalicious applications need to stay undetected as long as possible so victims can be infected without being caught\r\nby malware researchers, antivirus scanners or dynamic behavior-based analysis engines. To protect against the\r\nfirst two, malware is often packed, encrypted or obfuscated. For one, signature-based antivirus engines might fail\r\nto trigger even on known malware families when the sample is manipulated to a certain degree. Obfuscating the\r\nsample also increases the workload of threat researchers analyzing the malware manually, thus this either slows\r\nthem down or potentially prevents researchers from dissecting the malware altogether.\r\nThis is why one major advantage of dynamic behavior-based analysis is that the malware is executed in a\r\nsimulated environment which allows us to dynamically observe it’s behavior at runtime. As packed and encrypted\r\nsamples will at some point execute the original, unprotected executable, our system is able to automatically save a\r\nmemory dump of the unpacked binary. This is such a powerful feature that threat researchers rarely have to\r\nmanually unpack a malware to analyze it’s behavior. Instead, they can let VMRay Platform perform the\r\nunpacking.\r\nTo demonstrate this feature, we let VMRay Platform analyze a BumbleBee sample which is often protected by\r\nsuch measures. Once the dynamic analysis is done, we try to identify the memory dump containing the unpacked\r\nhttps://www.vmray.com/cyber-security-blog/understanding-bumblebee-the-malicious-behavior/\r\nPage 1 of 9\n\nbinary.\r\nAs we support multiple trigger reasons to dump a memory region (for example, when the memory content\r\nchanges, when the first network connection is established, when the application is terminated, etc.) there could be\r\nmultiple memory dumps to select from, many of which are not fully unpacked yet. The easiest method to find a\r\ngood memory dump is to select one with a YARA match, which implies that there must be enough strings and\r\ncode snippets to classify it as belonging to a certain malware family (see Figure 1 and Figure 2)\r\nAn even better approach is to find the memory dump for which the config extractor was triggered (see Figure 3).\r\nA successful config extraction is a stronger indicator for an unpacked binary.\r\nThis memory dump can now be analyzed by popular tools such as IDA Pro. It might be necessary to run it through\r\npe_unmapper first. To benefit from the information extracted during the analysis, we also have an IDA plugin that\r\nenriches the disassembly and decompilation with runtime information, such as function parameters observed\r\nduring execution (see here for more information).\r\nWhile this approach of unpacking malware has some limitations, e.g., packers employing virtual machine-based\r\nprotection such as VMProtect may never “unpack” the original executable as some of the code was replaced by\r\nvirtual operations by the protector, and thus this will prevent a memory dump containing the original instructions,\r\nVMRay Platform will still be able to dynamically observe the malware unhindered, as the original behavior will\r\nremain the same.\r\nMalicious behavior\r\nhttps://www.vmray.com/cyber-security-blog/understanding-bumblebee-the-malicious-behavior/\r\nPage 2 of 9\n\nThe main goal of a malware loader is to infect the system with additional malware, but most loaders also try to\r\nensure that the malicious executables are not downloaded or executed while being observed either by threat\r\nresearchers during manual analysis or by a behavior-based dynamic analysis system (see Figure 4).\r\nFor this purpose, BumbleBee includes more than 50 evasion techniques, ranging from tracking mouse movements\r\nto checking for artifacts of common virtualization tools such as VirtualBox. Our analysis shows that these\r\ntechniques were mostly copied from Al-Khaser, an open source collection of known evasion techniques.\r\nWe provide a list of all functions imported from Al-Khaser we have identified so far in the Appendix.\r\nNetwork\r\nTo download additional malware, BumbleBee makes contact with a remote C2 server. The oldest BumbleBee\r\nsample we could find uses HTTP as the network protocol while more recent versions have adopted WebSockets.\r\nOnce the connection is established, the infected system waits for one of seven possible commands.\r\nCommand name: shi\r\nFunction: Shellcode injection\r\nCommand name: dij\r\nFunction: DLL injection\r\nCommand name: dex\r\nFunction: Download \u0026 Execute\r\nCommand name: sdl\r\nFunction: Uninstall\r\nCommand name: ins\r\nFunction: Persistence\r\nhttps://www.vmray.com/cyber-security-blog/understanding-bumblebee-the-malicious-behavior/\r\nPage 3 of 9\n\nCommand name: gdt\r\nFunction: Execute shell commands\r\nCommand name: plg\r\nFunction: Load plugins\r\nWe have been able to observe that the last two commands were added somewhere around April and August 2022.\r\nInterestingly, the “plg” instruction is just a reference to the “dij” command, a hint that this functionality might be\r\nupdated in the future.\r\nEvasion techniques\r\nIn it’s most recent version, BumbleBee employs a total of over 50 evasion techniques, a majority of which are\r\nimported from the Al-Khaser open-source project.\r\nThey can be summarized in the following categories:\r\nDetecting virtualization software and related tools\r\nMost evasion techniques we have discovered are related to virtualization tools often used either during manual\r\nanalysis by threat researchers (VirtualBox, VMWare, Xen) or potentially used during dynamic, behavior-based\r\nanalysis, such as QEMU and KVM. One of the techniques, for example, checks if certain files such as\r\n“System32\\drivers\\VBoxMouse.sys” exist on the system to detect the presence of VirtualBox based on its drivers\r\n(see Figure 13).\r\nThere are also functions related to detecting Wine, a compatibility layer on Linux to execute Windows\r\napplications.\r\nDetecting reverse engineering tools\r\nhttps://www.vmray.com/cyber-security-blog/understanding-bumblebee-the-malicious-behavior/\r\nPage 4 of 9\n\nParticularly in older BumbleBee versions, we found checks for OllyDbg, a popular tool used by threat researchers\r\nto analyze malware and other Windows executables.\r\nThis check was removed in more recent versions, but newer samples still check for Process Explorer, another\r\nuseful utility sometimes used by threat researchers to explore processes running on the system.\r\nDetecting sandboxing artifacts\r\nTo detect some sandboxing solutions, BumbleBee checks if the currently logged-in username or it’s own filename\r\nis a name primarily used by sandbox technologies, for example “sample.exe” (see Figure 6).\r\nThis is one of the reasons VMRay Platform can randomize the username, the hostname and the filename (see\r\nFigure7). Additionally, one common evasion technique is checking if the filename is the hash of the file itself,\r\nwhich is often the case in dynamic analysis engines. This can also be prevented by randomizing the filename.\r\nhttps://www.vmray.com/cyber-security-blog/understanding-bumblebee-the-malicious-behavior/\r\nPage 5 of 9\n\nDetection via hardware configuration\r\nIn addition to searching for evidence that the sample is running inside of a virtualized or simulated environment,\r\nBumbleBee also checks the hardware of the system for specific configuration artifacts mostly associated with\r\nsandboxing.\r\nOne method checks if the RAM and the disk size are above a certain threshold, another checks if information\r\nabout the CPU fan can be retrieved.\r\nDetection via user behavior\r\nNot all evasion techniques rely on detecting the environment itself. Some smart techniques revolve around\r\ndetecting the presence of a user, which is usually not the case for automated sandbox solutions. In particular,\r\nBumbleBee checks if the mouse pointer moves (see Figure 8).\r\nVMRay employs a variety of techniques to simulate user behavior to avoid these evasion techniques from\r\ndetecting the monitored environment. For example, the mouse is moved regularly and we even simulate\r\ninteractions with the user interface. Additionally, our customers can also manually interact with the virtual\r\nenvironment during the analysis as if they were sitting in front of it – right from the web browser.\r\nCustom evasion techniques\r\nWe have discovered one evasion technique seemingly not covered by Al-Khaser: BumbleBee checks if it was\r\nstarted from the desktop (see Figure 9).\r\nThe reasoning here is that BumbleBee’s delivery chain usually results in the sample being located in, for example,\r\nthe temp directory or on a CD-ROM drive mounted from an ISO file, and not the desktop.\r\nhttps://www.vmray.com/cyber-security-blog/understanding-bumblebee-the-malicious-behavior/\r\nPage 6 of 9\n\nVMRay Platform allows customers to set the sample directory while uploading submissions (see Figure 10).\r\nNote that having multiple evasion techniques can actually backfire for the malware, as performing the evasion\r\ntechniques themselves can be detected as malicious behavior. For example, our VMRay Platform is able to\r\nobserve the checks for virtualized environments, which contributes to the final malicious verdict.\r\nThe evolution of BumbleBee\r\nWe have tracked BumbleBee since it first appeared in the wild and were able to create a rough timeline of when\r\nparticular important changes were introduced.\r\nIn summary, the network communication was changed from HTTP to WebSockets, and two new C2 operations\r\nwere introduced (see Figure 11) alongside nearly 20 additional evasion techniques. Notably, we have identified\r\nsamples where all evasion techniques were removed for a period of time around November 2022, but they were\r\nreintroduced later on (see Figure 12).\r\nhttps://www.vmray.com/cyber-security-blog/understanding-bumblebee-the-malicious-behavior/\r\nPage 7 of 9\n\nConclusion\r\nIn the world of cybersecurity, staying informed is our strongest shield. Our exploration of BumbleBee’s delivery\r\nmethods and malicious behavior has unveiled a landscape of complexity, where seemingly innocuous file formats\r\nare manipulated for malicious intent. With over 50 evasion techniques in its arsenal, BumbleBee showcases the\r\nevolving art of deception employed by threat actors.\r\nIn our upcoming article, we’ll delve deeper into BumbleBee’s behavior, exploring its configurations and the\r\nclusters emerging from our analysis. Stay tuned for the insights that fortify our understanding of this intricate\r\nmenace.\r\nAppendix\r\nEvasion Techniques imported from Al-Khaser\r\nvbox_files\r\nvbox_dir\r\nvbox_mac_wmi\r\nvbox_eventlogfile_wmi\r\nvbox_firmware_ACPI\r\nvbox_pnpentity_pcideviceid_wmi\r\nvbox_pnpentity_pcideviceid_wmi_2\r\nvbox_bus_wmi\r\nvbox_baseboard_wmi\r\nvbox_pnpentity_vboxname_wmi\r\nvmware_files\r\nvmware_firmware_ACPI\r\nqemu_dir\r\nqemu_firmware_ACPI\r\nhttps://www.vmray.com/cyber-security-blog/understanding-bumblebee-the-malicious-behavior/\r\nPage 8 of 9\n\nkvm_files\r\nknown_file_names\r\nknown_usernames\r\ndisk_size_wmi\r\nmodel_computer_system_wmi\r\nregistry_services_disk_enum\r\nget_services\r\ncheck_mac_addr\r\nGetProcessIdFromName\r\nget_system_firmware\r\nwine_reg_key\r\nwine_exports\r\nvbox_window_class\r\nvbox_reg_key_value\r\nvbox_reg_keys\r\nvbox_devices\r\nvbox_network_share\r\nvbox_processes\r\nvbox_window_class\r\nvbox_devices\r\nvbox_firmware_SMBIOS\r\nvmware_reg_keys\r\nvmware_mac\r\nvmware_devices\r\nvmware_firmware_SMBIOS\r\nvirtual_pc_process\r\nvirtual_pc_reg_keys\r\nqemu_reg_key_value\r\nqemu_processes\r\nqemu_firmware_SMBIOS\r\nkvm_reg_keys\r\nkvm_dir\r\nparallels_process\r\nmouse_movement\r\ncpu_fan_wmi\r\nmemory_space\r\nxen_check_mac\r\nSource: https://www.vmray.com/cyber-security-blog/understanding-bumblebee-the-malicious-behavior/\r\nhttps://www.vmray.com/cyber-security-blog/understanding-bumblebee-the-malicious-behavior/\r\nPage 9 of 9",
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