The Proton backdoor provides attackers with an almost full view of the compromised system, allowing the theft of browser information, keylogs, usernames and passwords, cryprocurrency wallets, macOS keychain data and more.
The compromise came to light on October 19, when cyber security researchers at ESET noticed the Elmedia Player was distributing Proton trojan malware. Users are warned if they downloaded the software from Eltima on that day before 3:15pm EDT, their system has may have been compromised by the malware.
If any of the following files or directories are on the system, it means the trojanised version of Elmedia Player is installed on the system.
Somehow, the attackers managed to build a signed wrapper around the legitimate media player which resulted in Proton being bundled along with it. Indeed, researchers say they observed the signing of the wrappers, all of which occurred with the same Apple Developer ID.
The ID has since been revoked by Apple and Eltima and ESET are working with Apple to find out how the malicious action was able to be taken in the first place. An Eltima spokesperson told ZDNet that while the malicious command and control server was registered on October 15, no malware was distributed until October 19.
For those unfortunate to fall victim to this attack - which only involved new downloads of Elmedia Player, automatic updates weren't compromised - the only way to get rid of the malware is to undergo a full OS re-installation.
Victims are also warned that they should take "appropriate measures" to ensure that their data can't be exploited by attackers.
Users are now able to download a clean version of Elmedia Player from the Eltima website, which ESET says is now free of compromise.
In response to the incident, Eltima says it has taken action to protect against future attacks and improve server security. An Apple spokesperson told ZDNet the company "at this stage we have nothing to add".