This is one of the most sophisticated malware campaigns I’ve ever encountered. In a nutshell, the malware is fed into a hotel’s network, waiting for specific individuals to log in. Once the target’s machine is infected, Darkhotel goes dormant for six months, then checks in at the home command and control server.

The Darkhotel actor maintains an effective intrusion set on hotel networks, providing ample access over the years, even to systems that were believed to be private and secure. They wait until, after check-in, the victim connects to the hotel Wi-Fi network, submitting his room number and surname at the login. The attackers see him in the compromised network and trick him into downloading and installing a backdoor that pretends to be an update for legitimate software – Google Toolbar, Adobe Flash or Windows Messenger. The unsuspecting executive downloads this hotel “welcome package”, only to infect his machine with a backdoor, Darkhotel’s spying software.

Once on a system, the backdoor has been and may be used to further download more advanced stealing tools: a digitally-signed advanced keylogger, the Trojan ‘Karba’ and an information-stealing module. These tools collect data about the system and the anti-malware software installed on it, steal all keystrokes, and hunt for cached passwords in Firefox, Chrome and Internet Explorer; Gmail Notifier, Twitter, Facebook, Yahoo! and Google login credentials; and other private information. Victims lose sensitive information – likely the intellectual property of the business entities they represent. After the operation, the attackers carefully delete their tools from the hotel network and go back into hiding.

Not clear if the Mac is vulnerable to Darkhotel. Clearly Windows is. Regardless, one lesson learned here is, when you travel, if you must use an unfamiliar/public network, assume that any update and software you download is tainted.