The Mutter Backdoor: Operation Beebus with New Targets

FireEye Labs has observed a series of related attacks against a dozen organizations in the aerospace, defense, and telecommunications industries as well as government agencies located in the United States and India which have been occurring at least as early as December of 2011. In at least one case, a decoy document included in the attack contained content that focused on Pakistan military advancements in unmanned vehicle, or “drone” technology.

Technically, these attacks exploited previously discovered vulnerabilities via document files delivered by email in order to plant a previously unknown backdoor onto victim systems. The malware used in these attacks employs a number of interesting techniques to “hide in plain sight” and to evade dynamic malware analysis systems. Similar to, though not based on the attacks we saw in South Korea, the malware tries to stay inactive as long as possible to evade dynamic analysis detection methods.


We have linked these attacks back to Operation Beebus through the C&C infrastructure along with the similar targets and timeline observed. Although some of the targets of these attacks overlapped with Beebus targets, there were many new targets discovered including some in India. As we uncover more targets related to these attacks, we are seeing a common link between them: unmanned vehicles, also known as “drones”. The set of targets cover all aspects of unmanned vehicles, land, air, and sea, from research to design to manufacturing of the vehicles and their various subsystems. Other related malware have been discovered through the same C&C infrastructure that have a similar set of targets, that when included bring the total number of targets to more than 20 as of this writing. These targets include some in academia which have received military funding for their research projects relating to unmanned vehicles.




All of the attacks we have observed occurred through document exploits attacking known vulnerabilities. We have seen RTF and XLS files used for delivery. Searching the internet for the author and document names yields information regarding South Asia politics. Although all of the document exploits we have analyzed drop a decoy document, most of them are either empty or filled with unreadable data with two exceptions.


One is an article about Pakistan’s indigenous UAV industry which is attributed to author Aditi Malhotra, an Indian writer and Associate Fellow at the Centre for Land Warfare Studies (CLAWS) in New Delhi. Although we are not sure this particular work is actually hers, we did find a reference to a similarly named article “Pakistan’s UAV programme: Ambitious, with some friendly help.” Unfortunately, this document was not available. Other works of hers on a similar note include “India’s Silence on Chinese Incursions” and “China and Pakistan: Dangerous Liaisons.”

The other decoy document is contact info for an American with a military provided email address from Joint Base Andrews in Maryland, but with a physical address in Pakistan titled “Family Planning Association of Base (FPAB).” It looks like they took the “Family Planning Association of Bangladesh” and combined it with “Joint Base Andrews.” The title of the email field is “FPAP Email”, “FPAP” could stand for “Family Planning Association of Pakistan.” Ultimately, we could make no sense from this information.


The Mutter Backdoor


Two different versions of the same backdoor were used in all of these attacks. In every case we have found, the main component is a DLL dropped by an executable compiled minutes after the DLL. The dropper shares the same decoding functions as the DLL and performs some modifications on the DLL that will be described later. There was one unique case we found where the initial dropper was a self-extracting archive that utilizes Visual Basic and batch scripts to download and install the DLL instead of extracting it from a resource.

Mutter is HTTP proxy aware, and attempts to determine if a proxy is required and what the proxy details are if necessary. It uses to perform such tests. It uses HTTP to communicate with the C&C server and expects an encoded string between a pair of <p> tags in the response. The URL in the request has one parameter, “i”, which is set to an encoded representation of a string that follows this format:

<Mutter version#>-<campaign marker?>-<victim hostname>-<victim IP address>

We are not certain about the second part of this string, it may be either a campaign marker or an extension of the version number. In all our cases, it is set to either “SN0” or “SN1." Actual strings are shared in the appendix information at the end of this blog.



This HTTP request pictured in the screenshot is from the older version of Mutter. The newer versions of Mutter have a very similar HTTP request, but with the Host and Connection headers swapped.

The response string is decoded and parsed for the following commands:

“m”: executes a shell command

“u”: uploads a file to the victim (downloads a file from the victim’s perspective)

“d”: downloads a file to the attacker (uploads a file from the victim’s perspective)

“R”: removes the auto-run registry value

These commands are referenced in the code in this order, and when said aloud it sounds like “mutter”, hence the name chosen for the malware. In the earlier version of this backdoor, the “d” command was referenced, but the code had not been implemented yet. In both versions, another command string “f” appears along with the others, but is not referenced in the code. This perhaps indicates a future feature to be added.

This malware employs several interesting evasion techniques. For starters, it employs several “hide in plain sight” techniques common to malware used in targeted attacks. It specifies fake properties, pretending to be Google or Microsoft.




This brings us to the next “hide in plain sight” tactic we noticed. Observe the size of the file above. It’s a whopping 41 megabytes. With rare exception, malware typically have a small size usually no larger than a few hundred kilobytes. When an investigator comes across a file megabytes in size, he may be discouraged from taking a closer look. Interestingly, the original size of this particular DLL is around 160 kilobytes, although the PE headers already indicate its future size as shown below. The dropper will decode this DLL from its resource section, drop it onto the victim’s system, and proceed to fill its resource section with randomly generated data. This has another useful side effect of giving each DLL a unique hash, making it more difficult to identify.


In addition to these hiding techniques, this malware also appears to employ techniques to possibly evade dynamic malware analysis systems. This has been an ongoing trend in malware development that we and others have observed several times in past. The malware author will add code to delay the execution of the important functionality for some period of time with the idea being that if the malware stalls for long enough, the dynamic malware analysis system will give up on it and pass it off as benign. This malware has two routines that we could find no other purpose than for such an evasion.

One routine is a function that simply runs a series of loops, incrementing a local variable over and over, thousands of times. It ultimately disregards the final value of this variable, meaning that the function serves no purpose. This function is called many times throughout the rest of the code. It may have been implemented for the purpose of wasting time.

Another routine seems to have a similar goal, but with a different approach. This time, a loop is implemented with a call to sleep for a short time. This loop occurs many times, and each time it will also allocate a chunk of memory on the heap, performing math operations on it and printing it to the console over and over again. Keep in mind that this memory is not initialized to any value and is not used for anything later in the code, it is essentially junk memory. This seems to be another means of wasting time.

We detect this malware as Backdoor.APT.NS01.


C&C Details


Most of the domains registered for C&C use in this campaign were done so through the free dynamic DNS Provider Dynamic DNS is a popular option for domain registration since it is free and provides a convenient level of anonymity.  Looking at passive DNS records for other domains pointing to the IP addresses used to host the C&C services turned up many other related domains. Various subdomains of the domain have pointed to several IPs pointed to by the Mutter domains. This is interesting because this is the name of the folder created by Mutter on victims’ systems. Furthermore, this domain is not a publicly available dynamic DNS provider and the email address used to register this domain is  We cannot be certain, but this name could be in reference to Binalakshmi Nepram, a writer-activist born in Manipur India who is fighting for disarmament. This fits the theme we have observed from other clues left behind in decoy documents. Another domain that is indirectly linked is with this interesting registration information.


Agni is the Hindu god of fire. Notice the combination of India and China references here. The email address used to register this domain was also referenced in a Chinese developer forum, but nothing else interesting was discovered about it.

The IP addresses hosting the C&C services are scattered all over the world and are believed to be compromised hosts.


Attackers, Targets, and Timeline


The attackers appear to be the well known and prolific “Comment Group” as we had stated in our previous blog on Operation Beebus. This link was made through finding several overlapping IP addresses used by Mutter and Beebus such as the following.


The theme of these attacks appears to be South Asia politics. The hints scattered throughout the documents and domain registrant information were laid on pretty thick which is something be wary of. The only legible, sensible decoy document observed so far is revealing of the interests of at least one of the targets of this campaign: namely the military threat of Pakistan against India and its growing relationships with other countries including China. The particular topic of this decoy document also appears to be a common link between most of the targets we have seen: unmanned vehicles.

The timeline below outlines the events specific to Mutter that we had visibility into. This campaign is still ongoing with Mutter callbacks being made to this day.





Exploit Document MD5 Exploit Exploit Document Filename Decoy Document Title Decoy Document Author Decoy Document Last Modified First Seen
b5f4a9aac67b53762ed98fafd067c803 b5f4a9aac67b53762ed98fafd067c803 CVE-2012-0158 CVE-2012-0158 NA NA Pakistan’s Indigenous UAV industry Pakistan’s Indigenous UAV industry GOPAL GURUNG GOPAL GURUNG Aug 2nd 2010 Aug 2nd 2010 Aug 27th 2012 Aug 27th 2012
92643bfa4121f1960c43c78a3d53568b 92643bfa4121f1960c43c78a3d53568b CVE-2008-3005 CVE-2008-3005 2012_3_12.xls 2012_3_12.xls NA NA NA NA Jan 26th 2003 Jan 26th 2003 Mar 22nd 2012 Mar 22nd 2012
4d5a235048e94579aab0062057296186 4d5a235048e94579aab0062057296186 CVE-2010-3333 CVE-2010-3333 Change of Address.doc Change of Address.doc Tele: 2619 4428 Tele: 2619 4428 kdly kdly Dec 6th 2011 Dec 6th 2011 Dec 7th 2011 Dec 7th 2011
589f10e2efdd98bfbdc34f247b6a347f 589f10e2efdd98bfbdc34f247b6a347f CVE-2010-3333 CVE-2010-3333 Urgent message.doc Urgent message.doc NA NA Administrator Administrator Feb 2nd 2003 Feb 2nd 2003 Mar 2nd 2012 Mar 2nd 2012
fd9777c90abb4b758b4aff29cfd68b98 fd9777c90abb4b758b4aff29cfd68b98 CVE-2012-0158 CVE-2012-0158 NA NA Tariq Masud Tariq Masud Haroon-ur-Rashid/Administrator Haroon-ur-Rashid/Administrator Sept 11 2012 Sept 11 2012    


Dropper Filename Dropper MD5 DLL Filename Mutex C&C Host Decoded “i” Value Compile Time
update.exe update.exe 725fc0d7a8e7b9e01a83111619744b6f 725fc0d7a8e7b9e01a83111619744b6f msdsp.dll msdsp.dll 654234576804d 654234576804d V0.9.6Y-SN1-<hostname>-<IP address> V0.9.6Y-SN1-<hostname>-<IP address> Aug 28th 2012 Aug 28th 2012
igfxtray.exe igfxtray.exe 681a014e9d221c1003c54a2a9a1d9df8 681a014e9d221c1003c54a2a9a1d9df8 winsups.dll winsups.dll mqe45tex13fw14op0 mqe45tex13fw14op0 V0.7-SN0-<hostname>-<IP address> V0.7-SN0-<hostname>h;-<IP address> Aug 28th 2012 Aug 28th 2012
NA NA 6aac76fc8309e29ea8a7afea48ae9b29 6aac76fc8309e29ea8a7afea48ae9b29 msdsp.dll msdsp.dll 654234576804d 654234576804d V0.9.6X-SN1-<hostname>-<IP address> V0.9.6X-SN1-<hostname>-<IP address> Aug 12th 2012 Aug 12th 2012
ctfmon.exe ctfmon.exe d5640ae049779bbb068eff08616adb95 d5640ae049779bbb068eff08616adb95 winsups.dll winsups.dll mqe45tex13fw14op0 mqe45tex13fw14op0 V0.7-SN0-<hostname>-<IP address> V0.7-SN0-<hostname>-<IP address> Aug 2nd 2010 Aug 2nd 2010
igfxtray.exe igfxtray.exe 681a014e9d221c1003c54a2a9a1d9df8 681a014e9d221c1003c54a2a9a1d9df8 winsups.dll winsups.dll mqe45tex13fw14op0 mqe45tex13fw14op0 V0.7-SN0-<hostname>-<IP address> V0.7-SN0-<hostname>-<IP address> Aug 2nd 2010 Aug 2nd 2010
igfxpers.exe igfxpers.exe 06d5dddd4c349f666d84a91d6edc4f8d 06d5dddd4c349f666d84a91d6edc4f8d msdsp.dll msdsp.dll NA NA NA NA NA NA    

Thanks to Darien Kindlund for his assistance in research.