A thorough investigation into reputed Chinese APT actor Winnti Group turned up a previously undocumented backdoor that was used to compromise a popular Asian mobile hardware and software vendor -- perhaps as a prelude to launching a major supply chain attack against its users.

Dubbed PortReuse, the modular malware is a passive network implant that piggybacks on an active process's open TCP port and then lays in wait for a "magic packet" before launching malicious activity, according to ESET researchers Marc-Etienne M.Léveillé and Mathieu Tartare in a newly released white paper and corresponding blog post. ESET does not specifically name the Asian tech company that was targeted by the malware, but does note that it did notify the company and has been collaborating on a remediation of the attack.

Also known as APT 41, Axiom and Blackfly, the Winnti Group has historically been tied to a number of prominent supply chain attacks that replace companies' legitimate software with weaponized versions in order to infect the machines that install them. Its members have often targeted game developers and their users, inserting backdoors into various games' build environments. Malware associated with Winnti Group include ShadowPad and, of course, Winnti, after which the ATP group is named. Recent incidents include supply chain attacks against CCleaner, NetSarang and Asus.

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