Microsoft introduced Data Protection Application Programming Interface (DPAPI) in Windows environments as a method to encrypt and decrypt sensitive data such as credentials using the…
The cybercrime group that brought us Satan, DBGer and Lucky ransomware and perhaps Iron ransomware, has now come up with a new version or rebranding named "5ss5c".
In a previous blog post, Satan ransomware adds EternalBlue exploit, I described how the group behind Satan ransomware has been actively developing its ransomware, adding new functionalities (specifically then: EternalBlue) and techniques with each run. Then, it appeared the group halted operations on at least the ransomware front for several months.
However, as it turns out, the group has been working on new ransomware - 5ss5c - since at least November 2019.
Name: cpt.dat URL: http://58.221.158[.]90:88/car/cpt.dat Purpose: ransomware MD5: 853358339279b590fb1c40c3dc0cdb72 SHA1: 84825801eac21a8d6eb060ddd8a0cd902dcead25 SHA256: ca154fa6ff0d1ebc786b4ea89cefae022e05497d095c2391331f24113aa31e3c Compilation timestamp: 2020-01-11 19:54:25 VirusTotal report: ca154fa6ff0d1ebc786b4ea89cefae022e05497d095c2391331f24113aa31e3c Fun fact: file version information contains "TODO: 5SS5C Encoder".
The compilation times are sequential, which makes sense - the downloader has been developed (and compiled) first, then the spreader and the actual ransomware.
Note that cpt.exe as filename has already been observed in Satan ransomware.
Further indicators, such as hashes, URLs, file paths and so on will be posted at the end of this blog post.
5ss5c - still in development - and with oddities
There's quite some curiosities that indicate 5ss5c is still in active development and stems from Satan ransomware, for example:
There are several logs created, e.g. there is a file "C:\Program Files\Common Files\System\Scanlog" that simply logs whether IPC SMB is open/available;
Certutil logging (successful download or not);
There are several Satan ransomware artefacts;
Other Tactics, Techniques and Procedures (TTP) align with both Satan (and DBGer), and slightly overlap with Iron:
One of these is, for example, the use of multiple packers to protect their droppers and payloads.
This time however, they decided to use both MPRESS and Enigma, and even Enigma VirtualBox! (Note: Enigma and Enigma VirtualBox are not the same - the latter is a virtualised packer and also referred to as EnigmaVM.)
However, there are quite some curiosities, one of them being what appear to be hardcoded credentials:
Figure 3 - Hardcoded creds
These hardcoded credentials will be leveraged in an attempt to connect to an SQL database with the xp_cmdshell command:
Curiously, we can identify the following data inside the ransomware in regards to the SQL database:
ecology.url
ecology.password
ecology.user
Searching a bit further, we can discover a company named Finereport (https://www.finereport.com/en/company), which claims to be "Top 1 in China’s BI market share in IDC "China BI Software Tracker, 2018". You guessed it - it uses SQL as database.
What else is new is, as mentioned before, the use of Enigma VirtualBox for packing an additional spreader module, aptly named poc.exe. This suggest they may be experimenting (poc often is an acronym for proof of concept).
This file will be dropped to C:\ProgramData\poc.exe and will run the following command:
cd /D C:\ProgramData&star.exe --OutConfig a --TargetPort 445 --Protocol SMB --Architecture x64 --Function RunDLL --DllPayload C:\ProgramData\down64.dll --TargetIp
Back to the actual ransomware. It will create the following mutexes:
SSSS_Scan (in previous iterations SSS_Scan has also been observed)
5ss5c_CRYPT
Just like its predecessor, 5ss5c also has an exclusion list, where it will not encrypt specific files as well as files in the following folders:
Figure 4 - Exclusion list
For example, the following folders belonging to Qihoo 360 (an internet security company based in China also offering antivirus) were already excluded in Satan and DBGer ransomware:
360rec
360sec
360sand
While these are new in 5ss5c ransomware:
360downloads
360safe
As in previous iterations, 5ss5c ransomware will stop database-related services and processes.
It will however only encrypt files with the following extensions:
This extension list is not like before, and includes mostly documents, archives, database files and VMware-related extensions such as vmdk.
The ransomware will then create the following URI structure to communicate with the C2 server (61.186.243[.]2):
/api/data.php?code=
&file=
&size=
&status=
&keyhash=
It will also create a ransomware note on the C:\ drive as: _如何解密我的文件_.txt which translates to _How to decrypt my file_.txt. Example content is as follows:
Some files have been encrypted If you want to retrieve the encrypted file, send (1) Bitcoins to my wallet If payment is not completed within 48 hours from the start of encryption, the amount of decryption will double. If you have other questions, you can contact me by email Your decryption credentials are: Email: [5ss5c@mail.ru]
Interestingly, the ransomware note does not contain a Bitcoin address. Additionally, the note only contains instructions in Chinese, not Korean nor English like previous iterations. Is 5ss5c ransomware more targeted, or just actively being tested by the group/developers behind it?
Encrypted files will have the actor's email address prepended and a unique token with the ransomware's name will be appended, for example; test.txt becomes [5ss5c@mail.ru]test.txt.Y54GUHKIG1T2ZLN76II9F3BBQV7MK4UOGSQUND7U.5ss5c.
Prevention
Enable UAC;
Enable Windows Update, and install updates (especially verify if MS17-010 is installed);
Install an antivirus, and keep it up-to-date and running;
Install a firewall, or enable the Windows Firewall;
Restrict, where possible, access to shares (ACLs);
Conclusion
Satan is dead, long live 5ss5c! It just doesn't sound as good, does it?
Whoever's behind the development of Satan, DBGer, Lucky and likely Iron ransomware, is back in business with the 5ss5c ransomware, and it appears to be in active development - and is trying to increase (or perhaps focus?) its targeting and spread of the ransomware.
It is recommended organisations detect and/or search for the indicators of compromise (IOCs) below, and have proper prevention controls in place. MITRE ATT&CK IDs can also be found below.
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