Security Experts:

New Mac OS X Botnet Taps Reddit For Command and Control

Researchers at Russian security firm Dr. Web have come across a new piece of malware which has already infected thousands of Mac OS X devices.

The threat, detected by the company as "Mac.BackDoor.iWorm," has been developed in C++ and Lua, and enables cybercriminals to execute a wide range of commands on infected machines. The backdoor can collect information on the infected system, download files, execute system instructions, and carry out other commands that are typical for botnets.

iWorm Mac MalwareWhat is interesting about Mac.BackDoor.iWorm is that it uses the social link-sharing site Reddit to get a list of command and control (C&C) servers.

"[In] order to acquire a control server address list, the bot uses the search service at, and—as a search query—specifies hexadecimal values of the first 8 bytes of the MD5 hash of the current date. The search returns a web page containing a list of botnet C&C servers and ports published by criminals in comments to the post minecraftserverlists under the account vtnhiaovyd," Dr. Web said in a blog post. "The bot picks a random server from the first 29 addresses on the list and sends queries to each of them. Search requests to acquire the list are sent to in five-minute intervals."

As security expert Graham Cluley explains, Reddit is not to be blamed for the fact that the malware is abusing its platform.

"[Reddit has] done nothing wrong as such, and even if they shut down the accounts that are communicating with the botnet there would be nothing to stop the hackers behind the campaign creating new accounts or using an alternative service (Twitter, perhaps?) to communicate with the compromised computers," Cluley said.

Dr. Web has also pointed out that the threat uses encryption in many of its routines.

As of September 29, the company had identified a total of 18,519 infected devices, over a quarter of them located in the United States. Infections have also been spotted in Canada, the United Kingdom, Spain, France, the Netherlands, Brazil, Mexico, Australia, Sweden and Russia. It's uncertain at this point how the malware is being distributed.

Earlier this week, researchers at Lacoon Mobile Security reported finding an iOS Trojan which they suspect could be used by the Chinese government against people taking part in the pro-democracy protests in Hong Kong. The malware, dubbed Xsser, is capable of stealing all sorts of sensitive information from infected iOS devices.

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Eduard Kovacs (@EduardKovacs) is a contributing editor at SecurityWeek. He worked as a high school IT teacher for two years before starting a career in journalism as Softpedia’s security news reporter. Eduard holds a bachelor’s degree in industrial informatics and a master’s degree in computer techniques applied in electrical engineering.