Researchers at Trusteer more than a week ago discovered a variant of the Citadel Trojan -- typically associated with stealing financial credentials -- targeting a major international airport's employees accessing their enterprise applications via the organization's VPN. The airport, which employs more than 15,000 people, has taken down its VPN site in response to the attack, and an investigation is under way.
"The configuration was not just targeting VPN access [to the airport's network], but a specific type of authentication" being used there, says Oren Kedem, director of product marketing for Trusteer, which is not naming the airport that was attacked.
"Somebody took the time to [set up] this attack," he says.
The airport is dropping its existing multifactor authentication method that the attackers were able to cheat, and looking at even stronger authentication methods. They had employed multifactor authentication that combined a PIN, CAPTCHA for selecting a known code by the user, and a one-time password generator.
Kedem says the use of Citadel in this manner rather than specifically for financial information-stealing was "unique."
The attackers used form-grabbing and screen capture methods to pilfer the victim user's username, password, and one-time passcode generated by the airport's authentication system. "The first part of the attack uses form grabbing to steal the username and password entered into the login screen. The second part of the attack relies on screen capture capabilities to take a snapshot of the image presented to the victim by the strong authentication product," Trusteer's Amit Klein wrote in a blog post today.
It's unclear just how the users were initially infected with the screen-grabbing malware, which targets Windows systems and kicks in when the user logs in and authenticates. "Once they have the credentials, they can use any computer anywhere in the world to access [the airport's] VPN," Kedem says. "Once they are in, they could go into other systems and get lists of employees."
Trusteer doesn't know who the attackers are and what they are after, but Kedem says they could be trying to gather intelligence on airport security processes, or even the border customs service.
He says the attack appears to be very targeted, and the bottom line is that VPN connections are not safe. "Since we've published this blog, we've had a lot of questions, such as if you added some additional tokens or SMS or some form of device fingerprinting, would that help here? The short answer is 'no,'" he says. "As long as an endpoint is infected, the VPN is simply not secure."
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