Trojan-Dropper:OSX/Revir.D

Summary

Trojan-Dropper:OSX/Revir.D silently drops other malicious programs onto the machine; on execution, Revir.D opens a decoy file to distract the user from the program's malicious activities.

Disinfection & Removal

Automatic Disinfection

Allow F-Secure Anti-Virus for Mac to remove the relevant files.

Technical Details

Trojan-Dropper:OSX/Revir.D is distributed as an application bundled, comprising the following components:

• The main binary - detected as Trojan-Dropper:OSX/Revir.D
• .conft - Contains an encrypted payload
• .confr - contains a decoy file. The first 2048 bytes are also used as the RC4 key to decrypt the payload
• .cnf - contains the filename to be used when creating the decoy file

Payload

Upon execution, the malware drops and executes its payload as the following:

• /tmp/Spotlight

In the samples analyzed, the payload contained another malware detected as Backdoor:OSX/Imuler.B; however, since Revir.D is an application bundle, other malware may be used in other samples.

Social Engineering

To distract the user from noticing its malicious activities, Revir.D drops a copy of the decoy file into the /tmp folder and opens it using the 'open' command. This command directs the OS X system to use the default application to handle the target file's filetype for this action. Unlike previous Revir variants, the decoy file is not limited to PDF (see Revir.A) or JPEG (see Revir.B).

For extra insurance, Revir.D drops another copy of the decoy file into the folder where the malware was executed, and then deletes itself. Presumably, this is done so that if users ever attempts to find the application they just executed, they would only find the decoy file instead.

Both copies of the decoy file use the filename specified in the .cnf component. If the .cnf component does not exist, the decoy files will use the default filename "TMPAAABBB."