USB Devices Can Crack Windows
By Paul F. Roberts
July 22, 2005
Vulnerabilities in USB drivers for Windows could allow an attacker to take control of locked workstations using a specially programmed Universal Serial Bus device, according to an executive from SPI Dynamics, which discovered the security hole.
The buffer-overflow vulnerabilities could enable an attacker to circumvent Windows security and gain administrative access to a user’s machine.
This is just the latest example of a growing danger posed by peripheral devices that use USB (Universal Serial Bus), FireWire and wireless networking connections, which are often overlooked in the search for remotely exploitable security holes, experts say.
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 Dynamics.
SPI is still testing the hole, and hasn’t informed Microsoft Corp. about the problem. The company will be demonstrating the vulnerability at this week’s Black Hat Briefings hacker conference in Las Vegas, but will not release details of the security hole, Sima said.
A spokesperson for Microsoft’s Security Response Center confirmed that the company has not received a vulnerability report from SPI. The company strongly encouraged any researcher to contact the MSRC if they have a vulnerability to report.
However, the flaw is with USB, not Windows, said David Dewey, a research engineer at SPI. Standards developed by the USB Implementers Forum Inc., the nonprofit corporation that governs USB, don’t consider security, he said.
For example, an attacker who knows of a vulnerability in a USB device driver can program one USB device—say a portable memory stick—to pose as the kind of device that uses the vulnerable driver, then plug the device into the host system and trigger the exploit when the host system loads the flawed driver, said Darrin Barrall, another SPI researcher.
Flaws in standard USB drivers aren’t hard to find, either, Dewey and Barrall said. “Like many hardware drivers, USB drivers are written with very little data validation and security awareness. They’re 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 tested attacks on Windows systems, but any operating system that is USB-compliant is probably vulnerable, he said.
Researchers at Safend, of Tel Aviv, Israel, have discovered similar holes in USB and other protocols used by peripheral devices, said CEO Gil Sever, demonstrating a USB storage device that is programmed to automatically copy recently accessed files when inserted into a Windows PC.
Attacks from peripheral devices usually require physical access to the host system, but janitors or contractors can easily exploit such access with a USB attack device, Sever said.
On Thursday, Safend released a beta version of Safend Protector, which allows companies to lock down or assign security policies to peripheral devices on Windows systems.
Companies like Microsoft are just beginning to consider the security threat from peripheral devices, even as developments like the USBIF’s Wireless USB standard will make it possible to remotely connect to PCs using high-speed, USB-based technology, Sever said.
But IT administrators, and an increasing number of companies, are waking up to the threat. DeviceLock (formerly SafeLine Inc.) of San Ramon, Calif. and Milan, Italy, and SecureWave S.A. of Luxembourg also sell technology that can secure peripheral or “end point” devices.
At Baptist Memorial Healthcare Corp., in Memphis, Tenn., IT administrators turned to Safend after some departments in the hospital network, such as Human Resources and Risk Management, started using portable USB “jump” drives to make backup copies of sensitive data after the hospital introduced new desktop systems that did not have floppy drives, said Lenny Goodman, director of the desktop management group at Baptist.
Goodman initially waited for Microsoft to address the problem by adding better features for controlling peripheral devices into Windows, but has been disappointed by the company’s lack of attention to the problem.
“I was really looking to them to address this issue, but Microsoft feels that this is a hardware issue and doesn’t see it as a problem,” he said.
Baptist, which operates 15 hospitals in Tennessee, Mississippi and Arkansas, has been using Safend’s USB auditing tool and will be providing users with encrypted, password-protected USB drives to do local backups.
The hospital is purchasing 6,000 licenses of Safend’s Port Protector product to block other, unauthorized peripheral devices, including insecure USB drives and iPods, he said.