Experts Warn of USB Risks

Windows driver vulnerability points to security hole.

Vulnerabilities in USB drivers for Microsoft Corp.s Windows could allow an attacker to take control of locked workstations by using a specially programmed USB device, according to an executive from SPI Dynamics Inc., a security vendor whose researchers discovered the security hole.

The vulnerabilities that could let an attacker circumvent Windows security and gain administrative access to the machines are the latest examples of a growing danger posed by peripheral devices that use USB, FireWire and wireless networking connections, experts say. They also underscore the need for security administrators to look beyond the obvious for threats to their networks.

The buffer overflow flaw is in device drivers that Windows loads whenever USB devices are inserted into computers running Windows 32-bit operating systems, including Windows XP and Windows 2000, said Caleb Sima, chief technology officer and founder of SPI, in Atlanta.

SPI is still testing the hole and hasnt informed Microsoft, of Redmond, Wash., about the problem. The company will be demonstrating the vulnerability at this weeks Black Hat USA conference in Las Vegas, but it will not release details of the security hole, Sima said.

The flaw lies within the USB protocol, not Windows, said David Dewey, a research engineer at SPI. Standards developed by USB Implementers Forum Inc., the nonprofit organization that governs USB, dont consider security, Dewey said.

For example, an attacker who knows of a vulnerability in a USB device driver can program one USB device—such as a portable memory stick—to pose as the kind of device that uses the vulnerable driver and then plug the device into the host system and trigger the exploit when the host system loads the flawed driver, said Darrin Barrall, an SPI researcher.

"Like many hardware drivers, USB drivers are written with very little data validation and security awareness. Theyre bare-bones drivers that focus on [speed]," Dewey said.

Best of all for attackers, the device drivers run with system-level privileges, giving an attacker full control of the host system once the exploit has been triggered. SPI researchers tested their attacks on Windows systems, but any operating system that is USB-compliant is probably vulnerable, Dewey said.

A spokesperson for Microsofts Security Response Center confirmed that the company has not received a vulnerability report from SPI. The company strongly encouraged researchers to contact the MSRC if they have a vulnerability to report.

Researchers at Safend Ltd., of Tel Aviv, Israel, have discovered similar holes in USB and other protocols used by peripheral devices, said CEO Gil Sever, as he demonstrated a USB storage device programmed to automatically copy recently accessed files when inserted into a Windows PC.


How many of these devices are connected to your LAN?

  • Apple Computer Inc. iPod With 20GB to 60GB drives on later models, iPods can easily be used to "slurp" data and files or to copy an entire disk image from corporate systems
  • PDAs and smart phones Bluetooth wireless connections can be used to transfer malicious code to laptops and desktops or to grab files, while built-in e-mail and instant messaging features provide an uncontrolled gateway to the rest of the Internet
  • Photo-smart printers With Ethernet and USB ports, these devices can be easily connected to corporate networks, but slots for a variety of portable media—such as memory sticks, CompactFlash and multimedia cards—could be used to introduce malicious code to a host system or network through the printer