Researcher from Webroot and Symantec posted about Mebromi rootkits findings. This is first ever BIOS rootkit Mebromi spread in wild. I am not sure how many of PC infected before the finding, I better switched to better OS. :)
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There are more and more known viruses that infect the MBR (Master Boot Record). Symantec Security Response has published a blog to demonstrate this trend last month. However, we seldom confront with one that infects the BIOS. One of them is the notorious CIH appeared in 1999, which infected the computer BIOS and thus harmed a huge number of computers at that time. Recently, we met a new threat named Trojan.Mebromi that can add malicious components into Award BIOS which allows the threat to take control of the system even before MBR.
The threat will drop a driver to %system%\drivers\bios.sys, then stop the beep service and replace %system%\beep.sys with the dropped one. After that it restarts beep service to load the dropped driver.
bios.sys is used to interact with BIOS such as get BIOS info, flash and backup BIOS.
By using bios.sys, the threat will check whether the compromised computer is using Award BIOS. If so, it will save existing BIOS to c:\bios.bin and check whether it is already infected:
READ FULL HERE
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In the past few weeks a Chinese security company called Qihoo 360 blogged about a new BIOS rootkit hitting Chinese computers. This turned to be a very interesting discovery as it appears to be the first real malware targeting system BIOS since a well-known proof of concept called IceLord in 2007. The malware is called Mebromi and contains a bit of everything: a BIOS rootkit specifically targeting Award BIOS, a MBR rootkit, a kernel mode rootkit, a PE file infector and a Trojan downloader. At this time, Mebromi is not designed to infect 64-bit operating system and it is not able to infect the system if run with limited privileges.
The infection starts with a small encrypted dropper that contains five crypted resource files: hook.rom, flash.dll, cbrom.exe, my.sys, bios.sys. The goal of these files will be presented later in this analysis.
The infection is clearly focused on Chinese users, because the dropper is carefully checking if the system it’s going to infect is protected by Chinese security software Rising Antivirus and Jiangmin KV Antivirus. To gain access to the BIOS, the infection first needs to get loaded in kernel mode so that it can handle with physical memory instead of virtual memory.
Many of you may recall the old CIH/Chernobyl infection, the infamous virus discovered in 1998 that was able to flash the motherboard BIOS, erasing it. Even CIH needed to gain kernel mode access to reach the BIOS, though at the time the virus was exploiting a privilege escalation bug in Windows 9x operating system which allowed it to overwrite the Interrupt Descriptor Table with its own payload from user mode, then triggering the overwritten interrupt handler and its malicious code is executed in kernel mode. Mebromi does not use such kind of privilege escalation trick anymore, it just needs to load its own kernel mode driver which will handle the BIOS infection. To do so, it uses two methods: it could either extract and load the flash.dll library which will load the bios.sys driver, or it stops the beep.sys service key, overwriting the beep.sys driver with its own bios.sys code, restart the service key and restore the original beep.sys code.
The bios.sys driver is the code which handle the BIOS infection. To read the BIOS code, it needs to map the physical memory located at physical memory address 0xF0000, this is where the BIOS ROM usually resides. Once read, the driver verifies if the BIOS ROM is Award BIOS, by checking the presence of the string: $@AWDFLA. If found, the driver tries to locate the SMI port that will be used by the rootkit to flash the BIOS ROM.
READ FULL HERE
**********************************
There are more and more known viruses that infect the MBR (Master Boot Record). Symantec Security Response has published a blog to demonstrate this trend last month. However, we seldom confront with one that infects the BIOS. One of them is the notorious CIH appeared in 1999, which infected the computer BIOS and thus harmed a huge number of computers at that time. Recently, we met a new threat named Trojan.Mebromi that can add malicious components into Award BIOS which allows the threat to take control of the system even before MBR.
The threat will drop a driver to %system%\drivers\bios.sys, then stop the beep service and replace %system%\beep.sys with the dropped one. After that it restarts beep service to load the dropped driver.
bios.sys is used to interact with BIOS such as get BIOS info, flash and backup BIOS.
By using bios.sys, the threat will check whether the compromised computer is using Award BIOS. If so, it will save existing BIOS to c:\bios.bin and check whether it is already infected:
READ FULL HERE
*******************************
In the past few weeks a Chinese security company called Qihoo 360 blogged about a new BIOS rootkit hitting Chinese computers. This turned to be a very interesting discovery as it appears to be the first real malware targeting system BIOS since a well-known proof of concept called IceLord in 2007. The malware is called Mebromi and contains a bit of everything: a BIOS rootkit specifically targeting Award BIOS, a MBR rootkit, a kernel mode rootkit, a PE file infector and a Trojan downloader. At this time, Mebromi is not designed to infect 64-bit operating system and it is not able to infect the system if run with limited privileges.
The infection starts with a small encrypted dropper that contains five crypted resource files: hook.rom, flash.dll, cbrom.exe, my.sys, bios.sys. The goal of these files will be presented later in this analysis.
The infection is clearly focused on Chinese users, because the dropper is carefully checking if the system it’s going to infect is protected by Chinese security software Rising Antivirus and Jiangmin KV Antivirus. To gain access to the BIOS, the infection first needs to get loaded in kernel mode so that it can handle with physical memory instead of virtual memory.
Many of you may recall the old CIH/Chernobyl infection, the infamous virus discovered in 1998 that was able to flash the motherboard BIOS, erasing it. Even CIH needed to gain kernel mode access to reach the BIOS, though at the time the virus was exploiting a privilege escalation bug in Windows 9x operating system which allowed it to overwrite the Interrupt Descriptor Table with its own payload from user mode, then triggering the overwritten interrupt handler and its malicious code is executed in kernel mode. Mebromi does not use such kind of privilege escalation trick anymore, it just needs to load its own kernel mode driver which will handle the BIOS infection. To do so, it uses two methods: it could either extract and load the flash.dll library which will load the bios.sys driver, or it stops the beep.sys service key, overwriting the beep.sys driver with its own bios.sys code, restart the service key and restore the original beep.sys code.
The bios.sys driver is the code which handle the BIOS infection. To read the BIOS code, it needs to map the physical memory located at physical memory address 0xF0000, this is where the BIOS ROM usually resides. Once read, the driver verifies if the BIOS ROM is Award BIOS, by checking the presence of the string: $@AWDFLA. If found, the driver tries to locate the SMI port that will be used by the rootkit to flash the BIOS ROM.
READ FULL HERE
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