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images/news/windows7.jpgA notorious rootkit that for years has ravaged 32-bit versions of Windows has begun claiming 64-bit versions of the Microsoft operating system as well.
The ability of TDL, aka Alureon, to infect 64-bit versions of Windows 7 is something of a coup for its creators, because Microsoft endowed the OS with enhanced security safeguards that were intended to block such attacks. The rootkit crossed into the 64-bit realm sometime in August, according to security firm Prevx.
According to research published on Monday by GFI Software, the latest TDL4 installation penetrates 64-bit versions of Windows by bypassing the OS's kernel mode code signing policy, which is designed to allow drivers to be installed only when they have been digitally signed by a trusted source. The rootkit achieves this feat by attaching itself to the master boot record in a hard drive's bowels and changing the machine's boot options.
“The boot option is changed in memory from the code executed by infected MBR,” GFI Technical Fellow Chandra Prakash wrote. “The boot option configures value of a config setting named 'LoadIntegrityCheckPolicy' that determines the level of validation on boot programs. The rootkit changes this config setting value to a low level of validation that effectively allows loading of an unsigned malicious rootkit dl file.”
The ability of TDL, aka Alureon, to infect 64-bit versions of Windows 7 is something of a coup for its creators, because Microsoft endowed the OS with enhanced security safeguards that were intended to block such attacks. The rootkit crossed into the 64-bit realm sometime in August, according to security firm Prevx.
According to research published on Monday by GFI Software, the latest TDL4 installation penetrates 64-bit versions of Windows by bypassing the OS's kernel mode code signing policy, which is designed to allow drivers to be installed only when they have been digitally signed by a trusted source. The rootkit achieves this feat by attaching itself to the master boot record in a hard drive's bowels and changing the machine's boot options.
“The boot option is changed in memory from the code executed by infected MBR,” GFI Technical Fellow Chandra Prakash wrote. “The boot option configures value of a config setting named 'LoadIntegrityCheckPolicy' that determines the level of validation on boot programs. The rootkit changes this config setting value to a low level of validation that effectively allows loading of an unsigned malicious rootkit dl file.”
