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A disconnected sandbox can miss malware behavior that depends on network access. In Khalif AL Mahmud’s analysis of FlexenseActivator.exe, an isolated virtual network with simulated services let the author observe a Windows connectivity check and subsequent network activity. Those findings concern one identified sample and setup—not every file with that name or every Trojan.Win32.Tiggre/Zpevdo sample.
What the investigation identified
AL Mahmud’s article, published August 25, 2025, identifies the analyzed file as FlexenseActivator.exe and attributes it to Trojan.Win32.Tiggre / Zpevdo. The reported SHA-256 is 18676ae2eaa48ac6037fa239d282acca0b6c7cd6c7d384abe6b5cd379f2c5e50. That hash is a more precise identifier than the filename: a same-named executable is not established as the same sample unless its hash matches.
The article says the file was distributed in pirated Flexense software archives. That describes the reported sample’s context; it does not establish that every archive or executable using the name is malicious. The author also reports that the executable was packed with UPX and had an entropy measurement of 7.916. Packing and a high entropy value can be useful analysis clues, but neither proves maliciousness by itself.
Why simulate an internet connection?
Some malware checks whether a system appears connected before attempting later network activity. If a sandbox has no network at all, a sample that waits on that check may stop early or appear less active. A simulated network can provide controlled responses without connecting the analysis machine to the public internet.
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AL Mahmud reports using an isolated Windows 10 analysis virtual machine connected to a REMnux gateway virtual machine over a host-only network. INetSim simulated network services, while FakeDNS redirected DNS requests. According to the author, the lab had no live internet access. The author’s repository describes isolated virtual machines and simulated services as part of the methodology and contains analyses, hashes and indicators of compromise—not malware binaries.
| Analytical condition | What it can reveal | Important limit |
|---|---|---|
| Disconnected sandbox | A sample’s local behavior and any activity it performs before a connectivity check. | Network-dependent actions may remain unobserved if the expected connection check fails. |
| Isolated sandbox with simulated services | In this case, the author reports observing the connectivity check and later network activity after simulated services responded. | This is the author’s account of one setup, not a controlled comparison or a guarantee that simulated responses will trigger all malware behavior. |
The distinction is useful when interpreting an apparently quiet run: “nothing happened” may mean the sample did not proceed under those conditions, not that the file is benign. Conversely, activity observed in a simulation does not by itself show what would happen on a real victim’s machine.
What the simulated connection exposed
A Windows connectivity check
AL Mahmud reports that the sample requested www.msftncsi.com/ncsi.txt, a Windows Network Connectivity Status Indicator (NCSI) check, and received a simulated HTTP 200 response. The author describes this as the sample asking, in effect, whether internet connectivity was available. The successful simulated response was followed by additional reported activity; the account does not establish that every sample with this family attribution uses the same sequence.
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In the expanded account of the network phase, the author describes DNS lookups redirected by FakeDNS and subsequent TLS connections used for certificate-chain checking. These are observations from the author’s sample and lab, not independently reproduced results. The use of simulated services matters: the traffic was observed in a contained environment and should not be read as a record of the sample reaching its intended live destinations.
Other behavior reported in the analysis
AL Mahmud also describes GoogleUpdater-like directories and processes, process injection into five GoogleUpdater processes and WMIADAP, and suspicious cleanup behavior. These are findings attributed to this analysis, not a checklist of traits guaranteed in all Tiggre/Zpevdo samples. The article does not make the mere presence of a legitimate updater directory or process conclusive evidence of infection.
The author presents the following as leads for investigation rather than standalone proof:
- Several GoogleUpdater version directories appearing where a system’s normal software history does not explain them.
- Unusual process arguments or process relationships involving updater-like processes or WMIADAP.
- Repeated NCSI connectivity checks in a suspicious process context.
- An unsigned executable re-executing from a temporary location, especially alongside other anomalous behavior.
- File or process cleanup activity that coincides with the suspicious execution.
Any one of these can have an innocent explanation. Investigators should evaluate them together with the file hash, signature status, process lineage, execution path, timestamps, network telemetry and other endpoint evidence rather than treating a name or directory as a verdict.
How to interpret the detection figures
AL Mahmud’s August 25, 2025 article reports that 33 of 76 antivirus vendors detected the sample on VirusTotal and cites a 100/100 Hybrid Analysis score. These are figures reported in that article, not current scan results; detection counts can change over time and depend on the exact file submitted.
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A separate Hybrid Analysis report for the sample is dated August 6, 2020 and lists a threat score of 55/100 and 46% AV detection. Those older report-specific figures are not directly interchangeable with the later article’s cited figures. Neither set establishes the file’s current detection status or the behavior of another file merely because its filename matches.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.What defenders can take from this case
- Identify the file precisely. Compare a file’s cryptographic hash with the reported SHA-256 before treating it as this sample. A filename alone is weak evidence.
- Preserve context. Record where the file came from, its signature status, execution path, parent process and relevant timestamps. These help distinguish an anomalous executable from a similarly named legitimate component.
- Look for connected evidence. Review process lineage and arguments, repeated NCSI requests, DNS and TLS telemetry, updater-like directories, and suspicious execution or cleanup patterns as a set.
- Interpret quiet runs cautiously. A sandbox without network connectivity may not expose behavior that follows a connectivity check. A simulated response can help an authorized analyst observe later stages, but the outcome remains specific to that sample and environment.
- Keep analysis isolated. The described method used virtual machines, a host-only connection and simulated services rather than live internet access. It is not a reason to run an untrusted executable on a normal workstation or expose it to an uncontrolled network.
The author’s GitHub repository provides the methodology summary and analysis write-ups, while the expanded network-phase account adds detail about DNS and TLS behavior. Both are presentations of AL Mahmud’s work, not independent replications. The 2020 Hybrid Analysis page is separate historical sandbox context, not proof that the same behavior will recur in another environment.
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