New MacOS Backdoor Distributed through Malicious Word Documents

A new MacOS Backdoor that embedded in malicious Word document has been likely distributed through phishing campaigns. Upon executing the documents it asks users to enable macros to download the final payload.

TrendMicro Researchers believe the backdoor is linked to hacking group OceanLotus, who responsible for launching high profile attacks against human rights organizations, media organizations, research institutes, and maritime construction firms.

Attackers targeted MacOS computers that have Perl modules installed. The MacOS Backdoor OSX_OCEANLOTUS.D is written in Perl programming language and the macro is obfuscated using decimal ASCII code.

The dropper is a persistent one and all the strings in the dropper are encrypted using an RSA256 key and custom base64-encoded.

MacOS Backdoor Functions

The backdoor contains two important functions.

infoClient – It collects the information and such as ComputerName, Mac OSX version, Owner’s name and checks for x86/ 64 bit.

runHandle – responsible for handling backdoor operations

All the data collected will be encrypted and then transferred to the C&C server. It scrambles it checks for the byte is odd or even and adds data according to it.

The scrambled data is to be encrypted again with randomly AES 256 key and the key is also scrambled with operation XOR 0x13 followed by ROL 6 operation.

Also, the final payload that obtained from the server also decoded again in a similar manner via decryption and scrambling.

How to stay safe – Business Phishing Campaign

1. Have a unique Email address.
2. Do not open any attachments without proper validation.
3. Don’t open emails voluntary emails.
4. Use Spam filters & Antispam gateways.
5. Never respond to any spam emails.
6. verify the vendor.
7. Implement Two-factor Authentication