Because TXT does not validate the SMM memory while software is being loaded, any malware that is hidden in SMM survives TXT's trusted launch process and can compromise the software that has just been launched.
Once compromised in that fashion, malware could completely bypass "everything the trusted boot is supposed to provide," Rutkowska said in an e-mail. "We can attack TXT only by combining those two [implementation and design flaws]."
"We used our SMM attacks to compromise the TXT boot process," Rutkowska said. "We could also use them to create SMM rootkits."
Rutkowska and Wojtczuk said that finding a way to compromise SMM is not easy, particularly on modern systems. But they said they have found several implementation errors in SMM that could allow an attacker to potentially introduce malicious code.
Specific details of some of the new SMM attacks will be presented later this year at the Black Hat conference in Las Vegas, after Intel has had a chance to patch the underlying vulnerabilities.
Rutkowska said Intel was in the process of patching its BIOS software to deal with vulnerabilities in the SMM software. But she said dealing with the TXT problem could be slightly trickier because it involves the development of something called the SMM Transfer Monitor, "a special hypervisor that should be written by OEM/BIOS vendors," in addition to Intel, also a BIOS vendor.
Spokesman George Alfs confirmed that Intel is working with the researchers on the issue. "We are not aware of any active exploits in the wild as described in their research, but we take all reports seriously," Alfs said.
Computerworld is an InfoWorld affiliate.