Windows Defender detects Trojan in produced binary

[jeroenpelgrims]

This is only detected in the binary that was added to the release by this build action.
When I build the executable manually then no issue is detected.
The binary produced by the action is also slightly larger than the one built locally. (I don't know if I used the same rust version though, that could have an effect)

In case you want to see the source for what I'm trying to build:
https://github.com/jeroenpelgrims/ynab-belfius

I've since removed the offending release from Github.

[Douile]

This is very alarming, would it be possible to link a virus total scan of the binary?

[jeroenpelgrims]

This is the report for the Windows binary:
https://www.virustotal.com/gui/file/3f62f9add12714eac79cb46512ad39a355964868ffb2a53bc6eafe2f28bc8d7a?nocache=1
This is the report for the Linux binary (this one's clean):
https://www.virustotal.com/gui/file/693f3f89837a2e360146b251d55ee782e80635d101cbc3d34121e66dbdb8dc6b?nocache=1

I've created a new release for this issue.
The original files can be looked at here: https://github.com/jeroenpelgrims/ynab-belfius/releases

For extra info, my initial comment only mentions 1 detection, but Windows defender showed me 2 threats in the same binary.

Also, this is the Virustotal result for a locally built release (clean, rustc v1.73.0):
https://www.virustotal.com/gui/file-analysis/MTBkMmMwZDQ2NGE4NWJjM2M2ZjZlODUwMDE5YWJmM2I6MTcwNzM0MjkyOA==

[Douile]

After a lot of testing I have found that any rust program cross-compiled on alpine linux linked using mingw-w64 seems to get the same detection: https://www.virustotal.com/gui/file/25e247564dc98cb64f386c3b791108467dcd6a69f676fb9587f519c9c8eff197 (I'm not sure if they get detected by windows defender as I don't have windows).

Compiling using cross-rs there is a different detection but the binary is still detected as malicious.

I believe that this is a false positive because the toolchain I used to replicate the detection would require one of the following to be compromised:

• docker.io/alpine
• apkpkg/rustup
• apkpkg/mingw-w64-gcc
• mingw itself: https://stackoverflow.com/questions/62364507/compiled-c-executable-is-detected-as-a-virus-by-windows-defender
• rustup toolchains
• My system

If u want to avoid any detections this might be possible by using github actions' windows runner (I haven't tested this):

jobs:
  build:
    runs-on: windows-latest
    steps:
      - uses: actions/checkout@v4
      - run: cargo build --release
      - uses: diamondburned/action-upload-release@main
        with:
          files: target/release/my-program.exe

[jeroenpelgrims]

I had to split up the build and the add-to-release since diamondburned/action-upload-release doesn't seem to support running on Windows, the paths are messed up.

I build on Windows, and then add the binary to the release on a linux job.

on:
  release:
    types: [created]

jobs:
  build:
    runs-on: windows-latest
    steps:
      - uses: actions/checkout@v4
      - run: cargo build --release
      - uses: actions/upload-artifact@v4
        with:
          path: ./target/release
          if-no-files-found: error
          retention-days: 1
          overwrite: true

  add_to_release:
    runs-on: ubuntu-latest
    needs: build
    steps:
      - uses: actions/download-artifact@v4
        with:
          path: .
      - uses: diamondburned/action-upload-release@main
        with:
          files: artifact/ynab-belfius.exe

But unfortunately... Same result. Both Virustotal and Windows defender seem to detect threats :(

https://www.virustotal.com/gui/file/9da5ec8b4cbc750d338e563fb5810148565d174d021ce7f9eb0b6acef43f425b?nocache=1

Thank you for the thorough analysis though.

[Douile]

Was there previous releases that were not detected?

[jeroenpelgrims]

No,

This is (one of) my first time(s):

• Using Github actions in general
• Using rust-build.action to make a release of rust code I wrote.

I don't have any previous experience with building a release this way.
The first detection was literally the first ever binary I managed to build through Github actions.

I'm also aware it might be something I'm doing wrong, but I can't really imagine what since building locally doesn't cause any issues.

[lokkju]

I'm having the same issue; did you discover anything further?

https://www.virustotal.com/gui/file/66d323f73314aeb211ab53aed19c658ca49e0152d7a6b548e44deb5f0b2fac44/behavior

[jeroenpelgrims]

Hi @lokkju ,
I haven't found anything more out unfortunately.
I only use rust in a few hobby projects of mine.

[michihupf]

Some context on this. This seems to be a problem with cross-compiling in general. I have tried to cross-compile a simple program to automatically accept the match when one it found for an online game (CS2). This binary is immediately nuked by Windows Defender as it thinks it contains Trojan:Win32/Wacatac.B!ml.

[mr-entropia]

Ran into the same issue. Binary is detected as Trojan:Win32/Wacatac.B!ml .