Feeds

Bank-raid ZeuS malware waltzes around web with 'valid app signature'

Check your vaults. Did someone just lose their secret software signing key?

Seven Steps to Software Security

A variant of the bank-account-raiding ZeuS Trojan is masquerading as a legit Windows app using a valid digital signature – and packs a rootkit to burrow deep into victims' PCs.

It appears miscreants have somehow gained access to the private signing key belonging to a Microsoft-registered third-party developer in Switzerland, and used it to cryptographically sign the malware's executable. This key should be kept a closely guarded secret.

The Windows operating system and antivirus tools can check the validity of a program's digital signature before trusting it, because an invalid signature indicates the code has been tampered with in transit, for instance. By generating a valid signature for the ZeuS Trojan from a trusted private key, crims can dress the software nasty up as a legit application.

It's a sign that crooks are adopting tactics used by sophisticated espionage software, such as Flame: signing binaries to slip code onto victims' machines is part and parcel of modern-day cyber-spying. The use of stolen certs by criminals is rare but not unprecedented.

Researchers at SSL-certificate flogger Comodo, using telemetry collected from users of its security software, detected 200 installs of this latest ZeuS variant.

ZeuS (aka Zbot) is typically distributed by hackers planting malicious code on legitimate websites that exploit browser bugs to install the nasty, or through email phishing by tricking netizens into running attachments.

The malware discovered by Comodo presented itself a web-page with the Internet Explorer logo on it, whereas it's really a malicious signed executable that drops an installer on the hard drive to run, which tries to download a rootkit from the web. This is decrypted into a driver and lined up to execute early on in the PC's boot sequence – meaning it can get to work hiding the Trojan from the rest of the operating system and applications, particularly tools that try to remove the Trojan.

When running, the software's goal is to intercept usernames and passwords, credit card numbers and other highly sensitive personal information submitted through website forms – particularly those on banking websites – and siphon the data off to crooks to exploit.

Richards Moulds, veep of product strategy at Thales e-Security, said that the digitally signed ZeuS binary undermines the system of trust that Windows and other operating systems rely on.

"Windows, iOS, Android, and Linux all use code signing to ensure that only legitimate, signed code is installed and executed," Moulds explained. "Code-signing provides the best mechanism for proving that code hasn’t been modified and therefore is a way of spotting malware infected software and rejecting it. If an attacker can sign their malicious code in a way that passes this validation process they are a huge step further in mounting an attack." ®

Mobile application security vulnerability report

More from The Register

next story
Yorkshire cops fail to grasp principle behind BT Fon Wi-Fi network
'Prevent people that are passing by to hook up to your network', pleads plod
HIDDEN packet sniffer spy tech in MILLIONS of iPhones, iPads – expert
Don't panic though – Apple's backdoor is not wide open to all, guru tells us
NEW, SINISTER web tracking tech fingerprints your computer by making it draw
Have you been on YouPorn lately, perhaps? White House website?
LibreSSL RNG bug fix: What's all the forking fuss about, ask devs
Blow to bit-spitter 'tis but a flesh wound, claim team
BMW's ConnectedDrive falls over, bosses blame upgrade snafu
Traffic flows up 20% as motorway middle lanes miraculously unclog
Attackers raid SWISS BANKS with DNS and malware bombs
'Retefe' trojan uses clever spin on old attacks to grant total control of bank accounts
Manic malware Mayhem spreads through Linux, FreeBSD web servers
And how Google could cripple infection rate in a second
Mozilla fixes CRITICAL security holes in Firefox, urges v31 upgrade
Misc memory hazards 'could be exploited' - and guess what, one's a Javascript vuln
prev story

Whitepapers

Designing a Defense for Mobile Applications
Learn about the various considerations for defending mobile applications - from the application architecture itself to the myriad testing technologies.
How modern custom applications can spur business growth
Learn how to create, deploy and manage custom applications without consuming or expanding the need for scarce, expensive IT resources.
Reducing security risks from open source software
Follow a few strategies and your organization can gain the full benefits of open source and the cloud without compromising the security of your applications.
Boost IT visibility and business value
How building a great service catalog relieves pressure points and demonstrates the value of IT service management.
Consolidation: the foundation for IT and business transformation
In this whitepaper learn how effective consolidation of IT and business resources can enable multiple, meaningful business benefits.