ESET researchers uncover a malware household with instruments that present indicators they’re utilized in focused assaults
ESET researchers have found a beforehand unknown malware household that makes use of customized and well-designed modules, focusing on programs working Linux. Modules utilized by this malware household, which we dubbed FontOnLake, are always beneath improvement and supply distant entry to the operators, accumulate credentials, and function a proxy server. On this blogpost, we summarize the findings revealed in full in our white paper.
To gather knowledge (as an illustration ssh credentials) or conduct different malicious exercise, this malware household makes use of modified legit binaries which might be adjusted to load additional parts. In reality, to hide its existence, FontOnLake’s presence is at all times accompanied by a rootkit. These binaries comparable to cat, kill or sshd are generally used on Linux programs and may moreover function a persistence mechanism.
The sneaky nature of FontOnLake’s instruments together with superior design and low prevalence counsel that they’re utilized in focused assaults.
The primary recognized file of this malware household appeared on VirusTotal final Might and different samples have been uploaded all year long. The situation of the C&C server and the nations from which the samples have been uploaded to VirusTotal would possibly point out that its targets embody Southeast Asia.
We imagine that FontOnLake’s operators are notably cautious since nearly all samples seen use distinctive C&C servers with various non-standard ports. The authors use principally C/C++ and numerous third-party libraries comparable to Increase, Poco, or Protobuf. Not one of the C&C servers utilized in samples uploaded to VirusTotal have been energetic on the time of writing – which signifies that they might have been disabled because of the add.
Recognized parts of FontOnLake
FontOnLake’s at the moment recognized parts might be divided into three following teams that work together with one another:
- Trojanized purposes – modified legit binaries which might be adjusted to load additional parts, accumulate knowledge, or conduct different malicious actions.
- Backdoors – consumer mode parts serving as the primary level of communication for its operators.
- Rootkits – kernel mode parts that principally conceal and disguise their presence, help with updates, or present fallback backdoors.
We found a number of trojanized purposes; they’re used principally to load customized backdoor or rootkit modules. Other than that, they will additionally accumulate delicate knowledge. Patches of the purposes are most probably utilized on the supply code stage, which signifies that the purposes will need to have been compiled and changed the unique ones.
All of the trojanized recordsdata are customary Linux utilities and every serves as a persistence methodology as a result of they’re generally executed on system start-up. The preliminary approach wherein these trojanized purposes get to their victims just isn’t recognized.
Communication of a trojanized utility with its rootkit runs by a digital file, which is created and managed by the rootkit. As illustrated in Determine 1, knowledge might be learn/written from/to the digital file and exported with its backdoor part upon the operator’s request.
The three completely different backdoors we found are written in C++ and all use, albeit in barely alternative ways, the identical Asio library from Increase for asynchronous community and low-level I/O. Poco, Protobuf, and options from STL comparable to good pointers are used as nicely. What’s uncommon for malware is the truth that these backdoors additionally function plenty of software program design patterns.
The performance that all of them have in widespread is that every exfiltrates collected credentials and its bash command historical past to its C&C.
Contemplating among the overlapping performance, most probably these completely different backdoors will not be used collectively on one compromised system.
All of the backdoors moreover use customized heartbeat instructions despatched and obtained periodically to maintain the connection alive.
The general performance of those backdoors consists of the next strategies:
- Exfiltrating the collected knowledge
- Making a bridge between a customized ssh server working regionally and its C&C
- Manipulating recordsdata (as an illustration, add/obtain, create/delete, listing itemizing, modify attributes, and so forth)
- Serving as a proxy
- Executing arbitrary shell instructions and python scripts
We found two marginally completely different variations of the rootkit, used solely one by one, in every of the three backdoors. There are vital variations between these two rootkits; nevertheless, sure points of them overlap. Although the rootkit variations are primarily based on the suterusu open-source challenge, they comprise a number of of FontOnLake’s unique, customized strategies.
Mixed performance of the 2 variations of the rootkit we found embody:
- Course of hiding
- File hiding
- Hiding itself
- Hiding community connections
- Exposing the collected credentials to its backdoor
- Performing port forwarding
- Magic packets reception (magic packets are specifically crafted packets that may instruct the rootkit to obtain and execute one other backdoor)
Following our discovery whereas finalizing our white paper on this matter, distributors comparable to Tencent Safety Response Middle, Avast and Lacework Labs revealed their analysis on what seems to be the identical malware.
All recognized parts of FontOnLake are detected by ESET merchandise as Linux/FontOnLake. Corporations or people who need to defend their Linux endpoints or servers from this menace ought to use a multilayered safety product and an up to date model of their Linux distribution; among the samples we’ve analyzed have been created particularly for CentOS and Debian.
Prior to now we described an operation that shared sure behavioral patterns with FontOnLake; nevertheless, its scale and influence have been a lot greater. We dubbed it Operation Windigo and you could find extra details about it in this white paper and this follow-up blogpost.
Further technical particulars on FontOnLake might be present in our complete white paper.
|38B09D690FAFE81E964CBD45EC7CF20DCB296B4D||Backdoor 1 variant 1|
|56556A53741111C04853A5E84744807EEADFF63A||Backdoor 1 variant 2|
|FE26CB98AA1416A8B1F6CED4AC1B5400517257B2||Backdoor 1 variant 3|
|D4E0E38EC69CBB71475D8A22EDB428C3E955A5EA||Backdoor 1 variant 4|
|204046B3279B487863738DDB17CBB6718AF2A83A||Backdoor 2 variant 1|
|9C803D1E39F335F213F367A84D3DF6150E5FE172||Backdoor 2 variant 2|
|BFCC4E6628B63C92BC46219937EA7582EA6FBB41||Backdoor 2 variant 3|
|515CFB5CB760D3A1DA31E9F906EA7F84F17C5136||Backdoor 3 variant 4|
|A9ED0837E3AF698906B229CA28B988010BCD5DC1||Backdoor 3 variant 5|
|56CB85675FE7A7896F0AA5365FF391AC376D9953||Rootkit 1 model 1|
|72C9C5CE50A38D0A2B9CEF6ADEAB1008BFF12496||Rootkit 1 model 2|
|B439A503D68AD7164E0F32B03243A593312040F8||Rootkit 1 model 3|
|E7BF0A35C2CD79A658615E312D35BBCFF9782672||Rootkit 1 model 4|
|56580E7BA6BF26D878C538985A6DC62CA094CD04||Rootkit 1version 5|
|49D4E5FCD3A3018A88F329AE47EF4C87C6A2D27A||Rootkit 1 model 5|
|74D44C2949DA7D5164ADEC78801733680DA8C110||Rootkit 2 model 1|
|74D755E8566340A752B1DB603EF468253ADAB6BD||Rootkit 2 model 2|
|E20F87497023E3454B5B1A22FE6C5A5501EAE2CB||Rootkit 2 model 3|
From internet-wide scan:
/and many others/sysconfig/modules/ati_remote3.modules
MITRE ATT&CK strategies
This desk was constructed utilizing model 9 of the ATT&CK framework.
|Preliminary Entry||T1078||Legitimate Accounts||FontOnLake can accumulate not less than ssh credentials.|
|Execution||T1059.004||Command and Scripting Interpreter: Unix Shell||FontOnLake permits execution of Unix Shell instructions.|
|T1059.006||Command and Scripting Interpreter: Python||FontOnLake permits execution of arbitrary Python scripts.|
|T1106||Native API||FontOnLake makes use of fork() to create extra processes comparable to sshd.|
|T1204||Person Execution||FontOnLake trojanizes customary instruments comparable to cat to execute itself.|
|Persistence||T1547.006||Boot or Logon Autostart Execution: Kernel Modules and Extensions||One in all FontOnLake’s rootkits might be executed with a start-up script.|
|T1037||Boot or Logon Initialization Scripts||FontOnLake creates a system start-up script ati_remote3.modules.|
|T1554||Compromise Consumer Software program Binary||FontOnLake modifies a number of customary binaries to realize persistence.|
|Protection Evasion||T1140||Deobfuscate/Decode Recordsdata or Data||Some backdoors of FontOnLake can decrypt AES-encrypted and serialized communication and base64 decode encrypted C&C handle.|
|T1222.002||File and Listing Permissions Modification: Linux and Mac File and Listing Permissions Modification||FontOnLake’s backdoor can change the permissions of the file it needs to execute.|
|T1564||Cover Artifacts||FontOnLake hides its connections and processes with rootkits.|
|T1564.001||Cover Artifacts: Hidden Recordsdata and Directories||FontOnLake hides its recordsdata with rootkits.|
|T1027||Obfuscated Recordsdata or Data||FontOnLake packs its executables with UPX.|
|T1014||Rootkit||FontOnLake makes use of rootkits to cover the presence of its processes, recordsdata, community connections and drivers.|
|Credential Entry||T1556||Modify Authentication Course of||FontOnLake modifies sshd to gather credentials.|
|Discovery||T1083||File and Listing Discovery||One in all FontOnLake’s backdoors can checklist recordsdata and directories.|
|T1082||System Data Discovery||FontOnLake can accumulate system data from the sufferer’s machine.|
|Lateral Motion||T1021.004||Distant Providers: SSH||FontOnLake collects ssh credentials and most likely intends to make use of them for lateral motion.|
|Command and Management||T1090||Proxy||FontOnLake can function a proxy.|
|T1071.001||Utility Layer Protocol: Internet Protocols||FontOnLake acquires extra C&C servers over HTTP.|
|T1071.002||Utility Layer Protocol: File Switch Protocols||FontOnLake can obtain extra Python recordsdata to be executed over FTP.|
|T1132.001||Knowledge Encoding: Normal Encoding||FontOnLake makes use of base64 to encode HTTPS responses.|
|T1568||Dynamic Decision||FontOnLake can use HTTP to obtain sources that comprise an IP handle and port quantity pair to hook up with and purchase its C&C. It could actually use dynamic DNS decision to assemble and resolve to a randomly chosen area.|
|T1573.001||Encrypted Channel: Symmetric Cryptography||FontOnLake makes use of AES to encrypt communication with its C&C.|
|T1008||Fallback Channels||FontOnLake can use dynamic DNS decision to assemble and resolve to a randomly chosen area. One in all its rootkits additionally listens for specifically crafted packets, which instruct it to obtain and execute extra recordsdata. It additionally each connects to a C&C and accepts connections on all interfaces.|
|T1095||Non-Utility Layer Protocol||FontOnLake makes use of TCP for communication with its C&C.|
|T1571||Non-Normal Port||Nearly each pattern of FontOnLake makes use of a novel non-standard port.|
|Exfiltration||T1041||Exfiltration Over C2 Channel||FontOnLake makes use of its C&C to exfiltrate collected knowledge.|