MAL-2026-10100 Malicious code in proxy-check-i (PyPI)

The package advertises itself as a wrapper for a 'qsshd executable' but the bundled Go binary is a reverse-SSH daemon that grants a remote operator persistent shell, exec, pty, and TCP port-forwarding on the installer's host. The entry point proxy-check-i (declared in the package's console_scripts, mapped to qsshd.launcher:main) uses os.execv to launch the bundled Go binary. The daemon establishes device identity by writing a .device_lock file under $XDG_CONFIG_HOME, /dev/shm, or /tmp, then repeatedly dials out to a relay via github.com/mydearniko/overthing (tunnel.NewServer with RelayURI and ForwardAddr pointing at the local SSH listener). SSH authentication only accepts a single hardcoded ed25519 public key embedded at build time via //go:embed authorized_keys, so only the key holder can connect. The reverse-connect design bypasses inbound firewalls. PyPI metadata is a cover story: PKG-INFO summary mentions only 'qsshd executable' with no README and no disclosure of SSH-server, authorized-keys, or outbound-relay behavior, so an installer cannot infer they are enabling a remote-shell daemon. Any host that runs proxy-check-i is remotely controllable by the key holder.

The embedded binary starts a relayed SSH-like server using a hardcoded authorized_key. Thanks to using a relay network, the attacked does not need to directly expose ports from the machine.

Category: MALICIOUS - The campaign has clearly malicious intent, like infostealers.

Campaign: 2026-07-proxy-check-i

Reasons (based on the campaign):

• backdoor

• The package contains code to execute remote commands (probably limited to a specific set) on the victim's machine.