On the heels of the ShellShock aka Bash disclosure that Mac OS X is included in the list of vulnerable operating systems comes word that hackers are using Reddit to connect Macs to a Botnet.
First let's start with what is a Botnet? A botnet is a collection of programs interconnected via the Internet communicating with other similar programs in order to perform tasks. When the program is installed on numerous computers, those programs depend on instructions from the command and control server they are connected to for information on tasks to be performed. They can be connected together by the command and control server to create a spam bot, where machines are brought together to send unwanted or malicious emails, or another example would be when a botnet is used in a DDoS (distributed denial of service) attack often against a government body or corporation.
Cyber criminals have developed a malware, dubbed Mac.BackDoor.iWorm, using C++ and Lua to open a backdoor into Mac OS X machines. When the malware is launched it saves it's configuration in a separate file and attempts to read the /Library directory, then uses system queries to determine the home directory of the Mac OS X account under which it is running, it then writes the data needed for it to continue to operate into this file. Next Mac.BackDoor.iWorm opens a port on the computer, sends a request to a remote site for a list of control servers, connects to the remote servers and then waits for instructions.
Reddit comes in to play as Mac.BackDoor.iWorm is using the search service at reddit.com to return results listing botnet C&C servers and ports published by the cyber criminals in the comments posted to minecraftserverlists under an account vtnhiaovyd. The malware, now a bot, picks a random server from the list to connect to. When the bot successfully connects to the server, it sends information about the open port on the machine it's infected as well as a unique ID for that machine that was created as a part of the configuration when it installed.
Now that machine waits for instructions from the Command and Control Server. As of the latest reports there is no evidence that these bots have received any instructions. Information obtained by Doctor's Web researches showed 17,658 computers had been infected by the malware and were part of the botnet as of September 26, 2014; a week later there are no available statistics for additional infected Macs. Of those infected over a quarter are in the US.
For anyone who continues to believe that Macs are safe and unaffected by viruses and malware, let this week be a wake up call. Previously Macs have been a less frequent target not due to their security, but due to their smaller market share. The more Macs on the market the more cyber criminals will be targeting them.