Zeus Targeting Mobile Phone Authentication

A new variant of the Zeus botnet aims to circumvent an increasingly popular mode of two-factor authentication among financial institutions and other enterprises.Anyone who has been following IT security long enough knows that it's a never ending game of leapfrog. As businesses and the security industry devise new ways to thwart attacks, criminal attackers find new ways to do their deeds. It's a game that's as old as crime itself, and I don't see it going away any time soon.

Enter the new variant of the infamous Zeus malware. According to Spanish security firm S21sec, Zeus authors have a plan to render an increasingly popular form of multi-factor less effective.

Increasingly banks and others are turning to mobile phone SMS texting features as a way to add a layer of additional authentication for users and transactions. For instance, last week when I used my online banking service to make a transfer to another customer the bank sent a code to my cell phone that I had to enter back online to complete the transaction.

Bad guys want to get in the middle of these transactions. From S21sec's security blog:

"In this post, we are going to talk about a better alternative planned by a ZeuS gang: infect the mobile device and sniff all the SMS messages that are being delivered. The scenario is now easier:

- The attacker steals both the online username and password using a malware (ZeuS 2.x)

- The attacker infects the user's mobile device by forcing him to install a malicious application (he sends a SMS with a link to the malicious mobile application)

- The attacker logs in with the stolen credentials using the user's computer as a socks/proxy and performs a specific operation that needs SMS authentication

- An SMS is sent to the user's mobile device with the authentication code. The malicious software running in the device forwards the SMS to other terminal controlled by the attacker

- The attacker fills in the authentication code and completes the operation.

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That's certainly worthy of note, and it shows that attackers aren't going to stand still. They never have, and they never will. Does this mean SMS is dead as a form of additional authentication? Absolutely not. It still significantly raises the bar for the bad guys.

Interesting, however, that this bad news for SMS authentication tactics hits around the same time that Google announces its going to support SMS text messaging to authenticate to its online applications.

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