Counterfeit installers to system compromise: Tracking a deceptive software download campaign

Microsoft Defender Experts is tracking an active malware campaign that uses counterfeit software-download websites to impersonate trusted vendors and distribute malicious installers. The campaign has targeted users looking to download popular software and has resulted in compromises across multiple organizations and industries, primarily affecting China-based operations of multinational organizations and Chinese-speaking users. Microsoft has observed victims across healthcare, manufacturing, gaming, technology, logistics, government, and education sectors.

Once executed, the malicious installers deploy malware that establishes persistence, attempts to weaken security protections, and communicates with attacker-controlled infrastructure. Microsoft assesses with moderate confidence that this activity is consistent with the publicly reported Silver Fox (also known as Yinhu, 银狐) fake software campaign but has not attributed it to a nation-state actor. Microsoft Defender detected and disrupted activity across multiple stages of the attack, including automated containment through attack disruption. Organizations should prioritize preventing downloads from untrusted software sources and ensure protections such as SmartScreen, network protection, tamper protection, and Microsoft Defender XDR are enabled to help identify, block, and respond to related activity.

Attack chain overview

The campaign follows a consistent attack chain from a spoofed vendor download page to a self-protecting, persistent implant. The stages below trace that chain — initial access, delivery, execution, persistence, privilege escalation, defense evasion, and command and control.

Campaign scope and targeting

Microsoft observed affected devices predominantly associated with China-based operations and Chinese-speaking users, consistent with the Chinese-language lure content and the .com.cn and .hl.cn infrastructure. Confirmed activity spans medical devices and healthcare, manufacturing, gaming, technology, logistics, government, and higher education across multiple organizations and industries.

Initial access: spoofed software-download sites

The entry point is a fraudulent software-download website that spoofs a legitimate vendor. In one case, endpoint telemetry captured a device navigating to the fake Razer page pc-razerzone[.]com[.]cn and downloading app_setup.6653004.zip from the delivery host gehie246[.]com/712down ; two content-distinct copies of the same-named archive were written within roughly 69 seconds — a direct observation of server-side payload regeneration.

Across the estate, FileOriginReferrerUrl telemetry ties each downloaded archive to the impersonation page that served it and to rotating delivery hosts ( yimxg25tiy[.]com/73inst , cc8ttkv35b[.]com/7qinst , n7b8t85zsg[.]com/ins711 ) and a suspected attacker-controlled Alibaba Cloud Object Storage Service (OSS) bucket. The lure domains predominantly use .com.cn , .hl.cn , and .cn and embed the impersonated brand name.

Delivery: a dynamically generated installer archive

The following examples illustrate how look-alike domains routed users to the same delivery infrastructure while preserving brand-specific lure pages.

When the user selects the download control, Microsoft Edge retrieves a malicious installer archive from a small set of dedicated delivery domains.

A defining characteristic is that the archive keeps the same filename while its hash changes on every download — a strong indicator the payload is generated server-side, per request. Microsoft observed families of same-named archives ( app_setup.* , zinst.* , zintall.* , intsoft.* , innstll.* ) whose contents differ across downloads while the delivery URL stays constant; the full validated hash set is in the indicators of compromise below.

Brand-impersonation infrastructure

The campaign runs a large, uniform set of vendor look-alike pages on .com.cn and .hl.cn domains, each cloning the real product’s branding and presenting a prominent “Download now” button. All funnel to the same delivery and payload infrastructure.

Although these domains impersonate unrelated vendors, they are not independently hosted. Infrastructure enrichment, corroborated by Microsoft telemetry where the two overlap, resolves them into two groupings. Six domains resolve within AS132839, spread across four unrelated netblocks and three registered country codes, and a common pair of nameservers. Two further domains resolve within AS8796 in a single /21, using a different nameserver pair. One additional domain is served through a content delivery network (CDN), concealing its origin. Because hosting and Domain Name System (DNS) are frequently bundled by the same reseller, these are best read as two consistent procurement channels rather than two independent corroborating signals.

The practical implication for defenders is that netblock- and geography-based grouping will miss these relationships, while Autonomous System Number (ASN)-level analysis surfaces them.The autonomous system remains constant even where the address space and registered country vary. These are shared commercial hosting and DNS providers carrying substantial unrelated tenancy, so the ASN and nameserver should be treated as hunting pivots, not blocklist entries.

The following capture shows a representative impersonation page served by the campaign. The pages are high-fidelity clones of a legitimate vendor’s site with a prominent download call-to-action.

Execution: a wrapped installer drops a randomized stage-one payload

The wrapper installer creates a randomized executable path while reusing stable payload content, making names unreliable but behavior and hashes useful for detection.

Opening the archive yields a wrapper installer whose name follows a generated pattern (for example, a_instapp83353001.exe or ainst8663586104.exe ).

Executing the wrapper creates and launches a stage-one payload at a randomized path under a world-writable or system location; the directory and file names are randomized, but the payload content is stable. The same stage-one 256-bit Secure Hash Algorithm (SHA-256) (676a2a7b94ca…) was observed under many names and paths.

The end-to-end chain is visible as a parent-to-child process tree: msedge.exe writes the archive, an archiving tool ( 7zFM.exe , 360zip.exe , or WinRAR.exe ) extracts it, the bundled wrapper runs, and the wrapper launches the randomized stage-one payload.

Payloads are masqueraded; Microsoft confirmed the masquerade through file metadata on the later-stage payload (SHA-256 6d6ba2bc…), staged at C:\Program Files (x86)\ \ . The binary’s version resource declares CompanyName: “Speech Processing Solutions GmbH”, FileDescription: “Philips Speech Driver Client Configuration”, OriginalFileName: PhilipsSpeechDriverConfiguration.exe, and ProductVersion: 4.7.471.07,while executing from a randomized directory under a randomized file name. The same resource retains an unfilled build-template placeholder, ProductName: “TODO: ”, indicating the version information was fabricated for the payload rather than inherited from genuine vendor software. Microsoft also observed svchost.exe executing from a non-system path ( D:\hellothere\svchost.exe ) rather than C:\Windows\System32 .

A payload staged under C:\ProgramData\ \ (SHA-256 c6100166…) carries the version metadata of the Indigo Rose TrueUpdate Client (OriginalFileName: tu_rt.exe, ProductVersion: 3.8.0.0) and exhibits that product’s runtime behavior, writing _ir_tu2_temp_* artifacts to the user’s temp directory on each execution. Dropped by the later-stage payload and launched repeatedly by the Task Scheduler service, it connects to an attacker-controlled Alibaba Cloud OSS bucket over Transport Layer Security (TLS) and writes a further payload to a second randomized C:\ProgramData\ directory — a legitimate update mechanism repurposed for payload delivery.

Alternate execution vector: Windows Installer (msiexec)

In parallel with the wrapped-installer chain, Microsoft observed a second execution vector that uses the Windows Installer service. The installer performs its intended function; what the campaign gains is execution under a signed, trusted Windows component. The extracted installer invokes msiexec.exe in embedded mode, which writes and launches a randomized executable into a world-writable C:\Users\Public\ \ directory, the same masquerade pattern as the wrapper chain, but delivered through msiexec.exe .

The behavior is consistent and repeated: more than twenty distinct payload names were written this way, spawned by a range of parents including msedge.exe , explorer.exe , and svchost.exe .

Persistence and recurring execution: disguised scheduled tasks

Persistence and recurring execution are achieved through scheduled tasks whose display names imitate routine IT or productivity jobs (for example “Deadline Mission Target” and “Hierarchy Tools Smooth Inventory”), each launching a specific payload staged under C:\ProgramData\ .

Each task launches a specific payload:

The persistent payloads are staged in locations such as C:\ProgramData\7fYptijy.exe , C:\ProgramData\zsMmvukD\beuv4Mie.exe , and C:\ProgramData\uwMUCYBN\SaYC4Mga.exe . Because the payloads are launched by the Task Scheduler service (parented to svchost.exe -k netsvcs -p -s Schedule ) and multiple staggered tasks run per device, affected hosts exhibit a characteristic ~60-second re-execution cadence.

Privilege escalation: SYSTEM scheduled task and process injection

To perform privileged actions such as writing Microsoft Defender exclusions, the malware creates a short-lived scheduled task that runs as SYSTEM ( SCHTASKS /Create … /RL HIGHEST /RU “SYSTEM” ), executes the privileged action, then immediately runs and deletes the task

The /RL HIGHEST /RU “SYSTEM” combination elevates the exclusion write to SYSTEM, and the create-run-delete sequence minimizes the footprint of the helper task. Process injection was also observed. A persistent campaign payload (SHA-256 1bd3662d…), launched from C:\ProgramData\ by the Task Scheduler service, created a remote thread in a legitimate user application moments after that application started — executing payload code inside the context of a trusted process. Microsoft Defender detected the activity as A process was injected with potentially malicious code .

The sequence below shows a single execution cycle end to end: the Task Scheduler service launches the payload, the payload immediately attempts command-and-control on two non-standard ports — both blocked at the host firewall — and, seventeen seconds later, injects into a user application within milliseconds of that application starting.

Defense evasion: disabling host protections

Follow-on payloads take a layered approach to weakening the host. They add sweeping Microsoft Defender path exclusions via PowerShell ( Add-MpPreference -ExclusionPath ) and the SYSTEM scheduled-task registry write;

delete volume shadow copies ( vssadmin delete shadows /all /quiet ) to inhibit recovery;

harden payload directories with icacls so standard users cannot remove the files;

and neutralize Windows Update by stopping and disabling wuauserv, UsoSvc, uhssvc, and WaaSMedicSvc, renaming update dynamic-link libraries (DLLs), and deleting the SoftwareDistribution cache.

A malicious Windows Defender Application Control policy was written to the code-integrity store on multiple devices; Microsoft Defender Antivirus detected the tamper behavior as Behavior:Win32/MpTamperGpDisableAVFriendly.A .

Command and control (C2)

A later-stage networking payload establishes command-and-control over application-layer protocols on non-standard ports — observed ports include 5090, 7031, 7032, 7088–7090, 8050, 28290, and 28300.

C2 endpoints comprise a set of six-character [.]net domains (iualef, oijfwe, euioxu, czijbh, wfmwsj, tbdqxq) and IP-and-port endpoints; a primary hub was observed on 202.95.14[.]237 (AS152194, CTG Server Limited). Payloads were observed beaconing to these endpoints with both successful and failed callbacks; the dedicated [.]net and IP-and-port C2 was intermittently unreachable while the same payloads still completed TLS connections to cloud object storage, consistent with a dedicated C2 tier that was often down while cloud-hosted staging remained live.

Detection and disruption

In observed environments, Microsoft Defender surfaced alerts across multiple stages and, where criteria were met, Attack Disruption engaged to contain affected devices and accounts.

Representative alerts include Modification attempt in Microsoft Defender Antivirus exclusion list , Compromised device (attack disruption) , A process was injected with potentially malicious code , Potential C2 connection behavior , Suspicious Task Scheduler activity , and Compromised account conducting hands-on-keyboard attack . The campaign is not purely automated. In a subset of environments, the automated execution was accompanied by interactive, hands-on-keyboard activity, which attack disruption engaged to contain.

Microsoft Defender also blocked the attempted Server Message Block (SMB) lateral movement to additional hosts ( Lateral movement using SMB remote file access blocked on multiple devices ) and detected the C2 connection behavior; the campaign’s C2 endpoints are included in the blocked indicator set.

Attack disruption contained the device and account; full eradication of persistence still required responder action.

Mitigation and protection guidance

Microsoft recommends the following mitigations to reduce the impact of this threat. Check the recommendations card for the deployment status of monitored mitigations.

Campaign-specific recommendations

Enforce Tamper Protection. It blocks exclusion and registry writes to Microsoft Defender even when the payload runs as SYSTEM — directly countering the throwaway SYSTEM scheduled-task technique this campaign relies on.

Hunt behavior, not file names. File names and hashes rotate on every download; pivot on the C:\Users\Public\ \ .exe and C:\Program Files (x86)\ \ .exe drop pattern, the Philips-Speech masquerade, and the stable stage-one and networking payload hashes.

Alert on the tamper sequence. A SYSTEM scheduled task writing HKLM\…\Windows Defender\Exclusions\Paths then self-deleting, vssadmin delete shadows /all /quiet , and disabling wuauserv, UsoSvc, WaaSMedicSvc and uhssvc are high-fidelity signals.

Treat look-alike download archives as malicious in web and mail flow. Block ZIPs named app_setup.* , zinst.* , zintall.* , intsoft.* , and innstll.* served from *.com.cn or *.hl.cn brand-look-alike domains and the /712down, /73inst, /7qinst, and /ins711 delivery endpoints.

Correlate download referrers. Use FileOriginUrl and FileOriginReferrerUrl to catch landing-page to delivery-host pairs even after individual domains rotate, and block the C2 IP:port set and .net C2 domains.

Microsoft Defender XDR hardening recommendations

Microsoft Defender XDR customers can turn on attack surface reduction rules to prevent several of the infection vectors of this threat. These rules, which can be configured by any user, offer significant hardening against targeted attacks. In observed attacks, Microsoft customers who had the following rules turned on could mitigate the attack in the initial stages and prevent hands-on-keyboard activity:

Block executable files from running unless they meet a prevalence, age, or trusted list criterion

Block execution of potentially obfuscated scripts

Block use of copied or impersonated system tools

Use advanced protection against ransomware

Microsoft Defender XDR detections

Microsoft Defender XDR customers can refer to the list of applicable detections below. Microsoft Defender XDR coordinates detection, prevention, investigation, and response across endpoints, identities, email, and apps to provide integrated protection against attacks like the threat discussed in this blog.

Customers with provisioned access can also use Microsoft Security Copilot in Microsoft Defender to investigate and respond to incidents, hunt for threats, and protect their organization with relevant threat intelligence.

Microsoft Security Copilot

Security Copilot customers can use the standalone experience to create their own prompts or run the following prebuilt promptbooks to automate incident response or investigation tasks related to this threat:

Incident investigation

Microsoft User analysis

Threat Intelligence 360 report based on MDTI article

Vulnerability impact assessment

These promptbooks can help analysts summarize affected entities, review alert timelines, and pivot on the IOCs included in this blog. Note that some promptbooks require access to plugins for Microsoft products such as Microsoft Defender XDR or Microsoft Sentinel.

Threat intelligence reports

Microsoft Defender XDR customers can use threat analytics reports in the Defender portal (requires license for at least one Defender XDR product) to get the most up-to-date information the malicious activity and techniques discussed in this blog. These reports provide the intelligence, protection information, and recommended actions to prevent, mitigate, or respond to associated threats found in customer environments.

Microsoft Defender XDR and Microsoft Sentinel customers can run the following queries. . The behavior-based queries continue to work even as filenames, hashes, and domains rotate.

Campaign payloads and loaders Surfaces execution or creation of the campaign’s stable stage-one, later-stage, persistent, networking, and loader binaries by SHA-256.

Randomized payload drop pattern Finds executables dropped into randomized folders under world-writable or system locations — the campaign’s stable staging behavior regardless of filename.

Microsoft Defender exclusion tampering Detects the SYSTEM scheduled-task and PowerShell routines that write sweeping Microsoft Defender path exclusions.

Recovery inhibition and Windows Update neutralization Surfaces shadow-copy deletion and the routine that stops, disables, or renames Windows Update service components.

Windows Installer (msiexec) embedded-mode execution Catches the parallel delivery vector where msiexec launches a randomized payload from a world-writable path.

Disguised scheduled-task execution Flags payloads relaunched by the Task Scheduler service from user-writable directories (the ~60-second re-execution loop).

Command-and-control connections Matches callbacks to the campaign’s C2 IP:port set and six-character .net C2 domains.

Malicious delivery domains and download endpoints Identifies connections to the dedicated delivery domains and the /712down, /73inst, /7qinst, /ins711 download paths.

MITRE ATT&CK techniques observed

This threat has exhibited use of the following attack techniques. For standard industry documentation these techniques, refer to the MITRE ATT&CK framework .

Indicators of compromise (IOC)

Prior reporting and OSINT sources — Silver Fox (also known as Yinhu, 银狐)

TweetFeed community indicator feed — weekly IOC export

AlienVault OTX pulse — campaign delivery infrastructure and C2 indicators

MalwareBazaar — campaign payload sample (aea879a0…)

MalwareBazaar — campaign payload sample (6dacf281…)

LGSRC public indicator repository

For the latest security research from the Microsoft Threat Intelligence community, check out the Microsoft Threat Intelligence Blog .

To hear stories and insights from the Microsoft Threat Intelligence community the ever-evolving threat landscape, listen to the Microsoft Threat Intelligence podcast .

Evaluate your AI readiness with our latest Zero Trust for AI workshop .

Microsoft 365 Copilot AI security documentation

How Microsoft discovers and mitigates evolving attacks against AI guardrails

September 1 4 min read Cybersecurity IR Workshop: The workshop you shouldn’t miss Cyber resilience starts before a crisis. Gain practical insights from DART to strengthen readiness and response.

Cybersecurity IR Workshop: The workshop you shouldn’t miss

August 28 16 min read TerminalFix campaign deploys a reverse tunnel through multistage intrusion Microsoft Threat Intelligence provides analysis of a ClickFix campaign that uses fake CAPTCHA prompts, DLL sideloading, and a reverse tunnel, with detections and hunting guidance.

TerminalFix campaign deploys a reverse tunnel through multistage intrusion

August 26 23 min read When AI infrastructure becomes the target: Securing gateways and control points Microsoft Threat Intelligence examines attacks on exposed AI workloads, including LiteLLM gateway exploitation, credential harvesting, persistence, and cryptomining activity.

When AI infrastructure becomes the target: Securing gateways and control points