{ "id": "64a9f936-d95c-4a4f-9c1e-ee1788283b81", "created_at": "2026-04-06T00:08:39.553169Z", "updated_at": "2026-04-10T03:34:00.278392Z", "deleted_at": null, "sha1_hash": "f0d21aed93e93a62966610cc283da19211ca0e4e", "title": "Exploitation of VMware Horizon Servers by TunnelVision Threat Actor", "llm_title": "", "authors": "", "file_creation_date": "0001-01-01T00:00:00Z", "file_modification_date": "0001-01-01T00:00:00Z", "file_size": 174021, "plain_text": "Exploitation of VMware Horizon Servers by TunnelVision Threat\r\nActor\r\nBy eSentire Threat Response Unit (TRU)\r\nArchived: 2026-04-05 23:46:27 UTC\r\nAdversaries don’t work 9-5 and neither do we. At eSentire, our 24/7 SOCs are staffed with Elite Threat Hunters\r\nand Cyber Analysts who hunt, investigate, contain and respond to threats within minutes.\r\nWe have discovered some of the most dangerous threats and nation state attacks in our space – including the\r\nKaseya MSP breach and the more_eggs malware.\r\nOur Security Operations Centers are supported with Threat Intelligence, Tactical Threat Response and Advanced\r\nThreat Analytics driven by our Threat Response Unit – the TRU team.\r\nIn TRU Positives, eSentire’s Threat Response Unit (TRU) provides a summary of a recent threat investigation. We\r\noutline how we responded to the confirmed threat and what recommendations we have going forward.\r\nHere’s the latest from our TRU Team…\r\nWhat did we find?\r\nIn early February 2022, we identified suspicious account creation and credential harvesting attempts on a\r\ncustomer’s endpoint. The activity was escalated and traced to a VMware Horizon server.\r\nThis server was operating an out-of-date version known to be vulnerable to Log4Shell (CVE-2021-44228).\r\nThe server itself was not publicly accessible but believed to be exposed to untrusted input routed from an\r\nInternet-facing system.\r\nAnalysis by our Threat Intelligence team indicates a strong link to TunnelVision, an activity cluster\r\noperated by an Iranian-aligned threat actor(s).\r\nAttribution to the TunnelVision activity cluster is supported by the following artifacts and observed Tactics,\r\nTechniques and Procedures (TTPs):\r\nCommon use of tunnel server 142.44.135[.]86\r\nObserved C2 domain activate-microsoft[.]cf utilizes a similar naming convention to known\r\nTunnelVision server microsoft-updateserver[.]cf and shares similar registration characteristics.\r\nTTPs (summarized below) observed in this case align with known TunnelVision behavior.\r\nThe summary of intrusion activity for TunnelVision is as follows:\r\nThe initial pivot from compromised Horizon server occurred using NTLM authentication for a\r\ngeneric administrator account.\r\nA backdoor account “DomainAdmin” is created on secondary systems using net command and then\r\nadded to local administrators' group.\r\nThe adversary then performs lateral movement using PSexec and RDP.\r\nCredentials are then harvested using Procdump.\r\nhttps://www.esentire.com/blog/exploitation-of-vmware-horizon-servers-by-tunnelvision-threat-actor\r\nPage 1 of 6\n\nMalware is written to C:\\Users\\DomainAdmin\\Desktop\\Drokbk.exe which creates service name,\r\n“SessionManagerService”.\r\nThe malware written to c:\\programdata\\SoftwareDistribution\\SessionService.exe communicates\r\nwith activate-microsoft[.]cf and GitHub.\r\nSysinternals and SSH tools are downloaded by the backdoor account using a web browser on\r\ncompromised systems.\r\nLastly, RDP tunneling is done using Ngrok to IP 142.44.135[.]86.\r\nHow did we find it?\r\nWe used eSentire MDR for Endpoint to identify post-exploitation TTPs.\r\nWhat did we do?\r\nOur 24/7 SOC alerted the customer and responded to isolate the host on the client's behalf. We\r\nautomatically blocked certain actions such as credential harvesting.\r\nOur Incident Handler team was engaged for further identification and containment actions.\r\nWhat can you learn from this TRU positive?\r\nIn a recent blog post, SentinelOne researchers linked TunnelVision’s activity to the deployment of\r\nransomware using n-day vulnerabilities including Log4Shell to access and compromise targets\r\nWhile overall exploitation of Log4Shell has diminished since peaking in December 2021 (see figure 1),\r\nopportunistic exploitation of VMware Horizon servers continues.\r\nWe responded to several cases of Horizon Log4Shell exploitation throughout January and February 2022\r\n(including this one).\r\nNetwork visibility determines the level of response effort required with regards to the exploitation of\r\nHorizon servers. It means the difference between identifying direct exploitation vs. just the ripple effects of\r\na threat actor with a network foothold.\r\nWhere we had network and endpoint telemetry on Horizon servers, we were able to react and\r\ncontain successful exploitation prior to lateral spread.\r\nWhere visibility was adjacent to these servers, we identified post-exploitation activity such as lateral\r\nmovement using compromised credentials.\r\nIn certain cases, vulnerable Horizon servers were not Internet-facing, but ultimately had exploit requests\r\nrouted to them from external gateways.\r\nhttps://www.esentire.com/blog/exploitation-of-vmware-horizon-servers-by-tunnelvision-threat-actor\r\nPage 2 of 6\n\nFigure 1 Log4J exploit events observed by MDR for Network, December 2021 to January 2022\r\nRecommendations from our Threat Response Unit (TRU) Team:\r\nLoader malware attempts to install other malware, so the priority should be to identify and investigate the\r\npresence of follow-on malware on systems. In addition, we recommend:\r\nEnsure any system which is directly exposed to the Internet or that handles untrusted data routed from\r\nInternet-facing systems is patched for Log4Shell (CVE-2021-44228).\r\nEnsure your security tools are monitoring critical servers such as VMware Horizon.\r\nThis should include network, endpoint, and log visibility to aid with detection, response, and\r\ncontainment activities.\r\nAsk Yourself…\r\nAre you monitoring for compromise of critical systems and follow-on actions?\r\nAre patches in place for actively exploited vulnerabilities?\r\nIf you’re not currently engaged with a Managed Detection and Response provider, we highly recommend you\r\npartner with us for security services in order to disrupt threats before they impact your business.\r\nWant to learn more? Connect with an eSentire Security Specialist.\r\nTo learn how your organization can build cyber resilience and prevent business disruption with eSentire’s Next\r\nLevel MDR, connect with an eSentire Security Specialist now.\r\nhttps://www.esentire.com/blog/exploitation-of-vmware-horizon-servers-by-tunnelvision-threat-actor\r\nPage 3 of 6\n\nGET STARTED\r\nABOUT ESENTIRE’S THREAT RESPONSE UNIT (TRU)\r\nThe eSentire Threat Response Unit (TRU) is an industry-leading threat research team committed to helping your\r\norganization become more resilient. TRU is an elite team of threat hunters and researchers that supports our 24/7\r\nSecurity Operations Centers (SOCs), builds threat detection models across the eSentire XDR Cloud Platform, and\r\nworks as an extension of your security team to continuously improve our Managed Detection and Response\r\nservice. By providing complete visibility across your attack surface and performing global threat sweeps and\r\nproactive hypothesis-driven threat hunts augmented by original threat research, we are laser-focused on defending\r\nyour organization against known and unknown threats.\r\nhttps://www.esentire.com/blog/exploitation-of-vmware-horizon-servers-by-tunnelvision-threat-actor\r\nPage 4 of 6\n\nBack to blog\r\nTake Your Cybersecurity Program to the Next Level with eSentire MDR.\r\nBUILD A QUOTE\r\nin this blog\r\nWhat did we find?How did we find it?What did we do?What can you learn from this TRU positive?\r\nRecommendations from our Threat Response Unit (TRU) Team:\r\nhttps://www.esentire.com/blog/exploitation-of-vmware-horizon-servers-by-tunnelvision-threat-actor\r\nPage 5 of 6\n\nSource: https://www.esentire.com/blog/exploitation-of-vmware-horizon-servers-by-tunnelvision-threat-actor\r\nhttps://www.esentire.com/blog/exploitation-of-vmware-horizon-servers-by-tunnelvision-threat-actor\r\nPage 6 of 6", "extraction_quality": 1, "language": "EN", "sources": [ "Malpedia" ], "references": [ "https://www.esentire.com/blog/exploitation-of-vmware-horizon-servers-by-tunnelvision-threat-actor" ], "report_names": [ "exploitation-of-vmware-horizon-servers-by-tunnelvision-threat-actor" ], "threat_actors": [ { "id": "d8af157e-741b-4933-bb4a-b78490951d97", "created_at": "2023-01-06T13:46:38.748929Z", "updated_at": "2026-04-10T02:00:03.087356Z", "deleted_at": null, "main_name": "APT35", "aliases": [ "COBALT MIRAGE", "Agent Serpens", "Newscaster Team", "Magic Hound", "G0059", "Phosphorus", "Mint Sandstorm", "TunnelVision" ], "source_name": "MISPGALAXY:APT35", "tools": [], "source_id": "MISPGALAXY", "reports": null }, { "id": "2bfa2cf4-e4ce-4599-ab28-d644208703d7", "created_at": "2025-08-07T02:03:24.764883Z", "updated_at": "2026-04-10T02:00:03.611225Z", "deleted_at": null, "main_name": "COBALT MIRAGE", "aliases": [ "DEV-0270 ", "Nemesis Kitten ", "PHOSPHORUS ", "TunnelVision ", "UNC2448 " ], "source_name": "Secureworks:COBALT MIRAGE", "tools": [ "BitLocker", "Custom powershell scripts", "DiskCryptor", "Drokbk", "FRPC", "Fast Reverse Proxy (FRP)", "Impacket wmiexec", "Ngrok", "Plink", "PowerLessCLR", "TunnelFish" ], "source_id": "Secureworks", "reports": null }, { "id": "1699fb41-b83f-42ff-a6ec-984ae4a1031f", "created_at": "2022-10-25T16:07:23.83826Z", "updated_at": "2026-04-10T02:00:04.761303Z", "deleted_at": null, "main_name": "Magic Hound", "aliases": [ "APT 35", "Agent Serpens", "Ballistic Bobcat", "Charming Kitten", "CharmingCypress", "Cobalt Illusion", "Cobalt Mirage", "Educated Manticore", "G0058", "G0059", "Magic Hound", "Mint Sandstorm", "Operation BadBlood", "Operation Sponsoring Access", "Operation SpoofedScholars", "Operation Thamar Reservoir", "Phosphorus", "TA453", "TEMP.Beanie", "Tarh Andishan", "Timberworm", "TunnelVision", "UNC788", "Yellow Garuda" ], "source_name": "ETDA:Magic Hound", "tools": [ "7-Zip", "AnvilEcho", "BASICSTAR", "CORRUPT KITTEN", "CWoolger", "CharmPower", "ChromeHistoryView", "CommandCam", "DistTrack", "DownPaper", "FRP", "Fast Reverse Proxy", "FireMalv", "Ghambar", "GoProxy", "GorjolEcho", "HYPERSCRAPE", "Havij", "MPK", "MPKBot", "Matryoshka", "Matryoshka RAT", "MediaPl", "Mimikatz", "MischiefTut", "NETWoolger", "NOKNOK", "PINEFLOWER", "POWERSTAR", "PowerLess Backdoor", "PsList", "Pupy", "PupyRAT", "SNAILPROXY", "Shamoon", "TDTESS", "WinRAR", "WoolenLogger", "Woolger", "pupy", "sqlmap" ], "source_id": "ETDA", "reports": null } ], "ts_created_at": 1775434119, "ts_updated_at": 1775792040, "ts_creation_date": 0, "ts_modification_date": 0, "files": { "pdf": "https://archive.orkl.eu/f0d21aed93e93a62966610cc283da19211ca0e4e.pdf", "text": "https://archive.orkl.eu/f0d21aed93e93a62966610cc283da19211ca0e4e.txt", "img": "https://archive.orkl.eu/f0d21aed93e93a62966610cc283da19211ca0e4e.jpg" } }