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OS X Backdoor Provides Unfettered Access to Mac Systems

A recently discovered Mac OS X backdoor that masquerades as a document converter can provide attackers with full control over a compromised system, Bitdefender security researchers say.

Dubbed Backdoor.MAC.Eleanor, the new piece of malware can also be used for cyber-espionage, and abuses Tor (The Onion Router) network for communication and control purposes. What’s more, security researchers discovered that every infected machine has a unique Tor address and that the attacker uses it to connect and download malware.

The malicious program hides within seemingly legitimate software dubbed EasyDoc Converter, but which does nothing more than download a malicious script. As soon as a machine has been compromised, the backdoor provides the attacker with full access to the operating system, to file explorer, shell execution, webcam, and other resources, Bitdefender researchers explain in a new report (PDF).

The script executed by the fake app acts as an installer, but not before checking whether Little Snitch has been installed and whether the machine isn’t already infected. The malware installs its components in the “/Users/$USER/Library/.dropbox” directory, after which it registers them to system startup. The installed components include a Tor hidden service, a Web Service (PHP), and a PasteBin agent.

The Web Service (PHP) component is the backdoor that provides the attacker with control over the infected machine, while the Tor hidden agent is used to communicate with this component. The Tor hidden service offers access to a SSH local service as well, but it wasn’t found on the infected machine, and researchers believe that it might be added later.

The backdoor’s control panel, accessible through a Tor-generated address, provides the attacker with options such as File manager (view, edit, rename, delete, upload, download, archive, etc), Command execution, Script execution (php, perl, python, ruby, java, c), Shell via bind/reverse shell connect, Simple packet crafter, Connect to DBMS (mysql, sqlite, pdo), Process list/Task manager, Send mail with attachment (you can attach local file on server), and String conversion.

The malware can also be used to capture images and videos using the machine’s webcam, and can also view the captured content using a Tor address. An agent in the malware is meant to gather infection information, to update and fetch files from the user’s computer, or execute shell scripts. It can be used to fetch the images and videos captured with the machine’s camera.

The PasteBin Agent is used to store the machine’s unique Tor address to Each of the infected Macs has its own address that the attacker uses for control purposes, and all of them are encrypted with a public key using RSA and base64, before being uploaded to PasteBin, researchers say.

Bitdefender researchers managed to pinpoint April 19 as the date when the first infection info was uploaded to, which suggests that Eleanor is rather new. However, since the analyzed sample used a user limited to 25 uploads, the researchers couldn’t deduce the number of infected machines, because different samples might use different users and some of them might upload more than 25 entries.

“This type of malware is particularly dangerous as it’s hard to detect and offers the attacker full control of the compromised system,” says Tiberius Axinte, Technical Leader, Bitdefender Anti-malware Lab. “For instance, someone can lock you out of your laptop, threaten to blackmail you to restore your private files or transform your laptop into a botnet to attack other devices. The possibilities are endless.”

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