Recent attacks that use the increasingly popular Zeus Trojan are
demonstrating that widely used methods of out-of-band
authentication might be flawed, experts say.
New attack techniques dubbed "Man in the Mobile" (MitMo) are
allowing black hats to leverage malware placed on mobile devices to
get around password verification systems that send codes via SMS
text messages to users' phones for confirmation of identity.
"In a transaction verification system, the customer receives a text
message with the transaction details and a code to enter back into
the website -- only if the transaction details match the real
transaction," explains Mickey Boodaei, CEO of Trusteer.
"Transaction verification was considered a good solution to protect
against [MitMo] attacks, where malware attempts to submit a
transaction on behalf of the victim.
"However, MitMo completely bypasses this, as it controls the mobile
device and can forward the verification text to the fraudsters and
delete it from the device without letting the victim see it,"
Boodaei warns.
The expansion of Zeus' capabilities to carry out MitMo attacks is
yet another step in the cat-and-mouse game that banking security
professionals continue to play with hackers to ensure users are who
they say they are.
"[Banks] will need to adjust to the reality that two-factor
authentication will always be challenged by hackers. A compromised
mobile phone is the same as a compromised PC," says Derek Manky,
project manager for Fortinet's Cyber Security & Threat Research
unit.
Banks need to find ways to educate users and help them secure their
channels of authentication, Manky says. "End users may be aware of
the fact that they can have their account information stolen from
an infected PC and/or phishing attack, but likely won't think twice
about mobile attacks at the moment," he warns.
While education is certainly an important component, Boodaei
believes banks need to offer users a helping hand in securing those
channels for authentication.
"Banks should use technologies to secure the communication between
customers' computers and websites and between customers' mobile
phones and websites," Boodaei says.
"This requires an additional layer of security on the computer and
the mobile device, which can shield the communication and prevent
malware from accessing financial data and login information,"
Boodaei continues. "Many banks, such as Santander, the Royal Bank
of Scotland, HSBC, CIBC, SunTrust, and Fifth Third are already
offering this extra layer of security."
Organizations might also need to think more closely about the type
of out-of-band one-time-password technology they're using to boost
authentication, experts say. For example, a system where the user
directly replies to the SMS text through their phones -- rather
than simply entering a code supplied by text back into the Web
browser -- could be more secure. Or organizations could consider
forgetting about texts altogether and choose to go with an
old-fashioned phone call as the means for out-of-band
verification.
"We're not aware of any attacks that defeat this mechanism," says
Steve Dispensa, CTO and co-founder of PhoneFactor. "Because of the
logical separation between voice and data functions on smartphones,
phone calls are resistant to malware running on the phone."
Truly security-conscious organizations could even layer a further
factor into that phone call if they choose to add voice biometrics
checks into their verification calls. It's all a matter of
priorities. As Dispensa puts it, even the types of out-of-band
authentication that are vulnerable to these latest attacks are
still more secure than many other classes of two-factor
authentication that require less work to subvert.
"All token-based solutions, grid cards, etc., can be compromised
through a single piece of malware," Dispensa observes. "New
attacks, even in their most virulent forms, require two coordinated
infections -- to the user's mobile phone and to their computer.
This is substantially more difficult to achieve in practice."
"Legacy two-factor systems, such as security tokens, are fatally
flawed and routinely compromised, since it only takes a single
piece of malware to get around them," Dispensa cautions.
"Out-of-band two-factor technology is the new best practice, and we
expect to continue to see significant adoption. With 40-some
percent of PCs infected with malware, using a phone for
authentication is much more secure."
With more malware being spread to smartphones, however, this
advantage might not last forever, experts say.