Last week SaferNet reported on the return of Emotet, but it was unclear who was behind the comeback. Now it’s evident that the play may be a power-grab by the Conti Ransomware gang.
Security researchers at Advanced Intelligence stated in a report that restarting the project was driven by vacuum Emotet left after law enforcement agencies took it down. During its peak, it offered high-quality initial access to a number of ransomware operations.
Emotet was considered the most widely distributed malware and acted as a loader to other malware groups.
Qbot and TrickBot, in particular, were Emotet’s main customers and used their access to deploy ransomware (e.g. Ryuk, Conti, ProLock, Egregor, DoppelPaymer, and others).
“Emotet’s strategic, operational, and tactical agility was executed through a modular system enabling them to tailor payload functionality and specialization for the needs of specific customers” AdvIntel said in their report.
Many malware operators depended on Emotet for deployment, and the Emotet-TrickBot-Ryuk triad was commonplace in attacks.
Ryuk Ransomware itself served as the genesis of Conti Ransomware. Late last year, Conti Ransomware emerged as a new leader in the field while Ryuk attacks became far less common. The operators of both ransomware strains have a long history of attacks hitting organizations in the healthcare and education sector.
AdvIntel researchers say that once Emotet disappeared from the scene, top-tier cybercriminal groups, like Conti Ransomware (loaded by TrickBot and BazarLoader) and DoppelPaymer (loaded by Dridex) were left without a viable option for high-quality initial access.
“This discrepancy between supply and demand makes Emotet’s resurgence important. As this botnet returns, it can majorly impact the entire security environment by matching the ransomware groups’ fundamental gap”, AdvIntel stated.
With competitors leaving the ransomware business, the “traditional groups” such as Conti (previously Ryuk) and EvilCorp climbed up the ladder once again, attracting “the talented malware specialists who are massively leaving disbanded RaaSes.”
AdvIntel revealed that the Conti Ransomware gang, and at least one former Ryuk member, entered a partnership with Trickbot to make a plea to the remaining Emotet operators for a comeback.
AdvIntel researchers are confident that the Conti group will deliver their payload to high-value targets via Emotet once the botnet grows, and will become a dominant player on the ransomware scene.
Since partnerships yield the best results, as shown by the Emotet-TrickBot-Ryuk alliance in 2019 and 2020, a new triad may soon rise above other operations, with Conti ransomware as the final payload.
While Conti Ransomware has certainly seen an active 12 months, infections are expected to skyrocket with Emotet back in the mix.
Conti Ransomware Analysis
Note: The Analysis of Conti Ransomware was carried out by researchers at Vipre Labs.
Conti ransomware encrypts the files of their victims and publishes the data on their website similar to what other strains do. This extortion behavior is visible on their ransom note saying “We’ve downloaded your data and are ready to publish it on our news website”.
When executed, it will start to encrypt files and change the file extension of the encrypted files to .ODMUA. Like other ransomware, it will leave a ransom note that has a filename “readme.txt”.
The Conti ransomware website has an instruction on how to upload the README.txt for the decryption and a contact button at the bottom left of the page. Once you click the contact button, a form will appear where you will provide your contact information and question as shown below.
Conti ransomware will perform a known malware technique called process hollowing. It is where the malware will create a process in a suspended state, unmaps or removes the PE image layout from a given process space using ZwUnmapViewofSection function, write it’s malicious code using WriteProcessMemory, set a new entry point using SetThreadContext, and resume the execution of the suspended process using the ResumeThread function.
Upon research, we found out that the use of -p argument is to encrypt a specific directory with a single thread and the -m argument is to encrypt the files with multiple threads. It means that Conti ransomware has a multi-threading capability. Multi-threading is where main ransomware creates child threads to speed up the encryption.
It will use a string “hsfjuukjzloqu28oajh727190” that was decrypted using the decryption of string routine mentioned above for creating a mutex using CreateMutexA function. Then check if there’s an already running mutex. This was commonly used by ransomware to avoid infecting the system more than once.
It will also delete all the shadow volume copies on the infected system to ensure that the victims won’t be able to recover their encrypted files.
After deleting the shadow copies, Conti ransomware will now start its file encryption by first creating the ransom note which will be first drop in C drive using “CreateFileW” and write the content of its ransom note using “WriteFile”.
As with other ransomware, it will utilize the functions “FindFirstFileW” and “FindNextFileW” to find the files they will encrypt. Conti ransomware has a list of files/file extension and directories which will be excluded for the infection.
When Conti finds the file to be encrypted, it will now generate keys that will be used to encrypt the files. It will used the handle returned by calling the function “CryptAcquireContext” that request a cryptographic context from the Microsoft Enhanced Cryptographic Provider, then the “CryptGenRandom” function to generate cryptographically random bytes, and “CryptEncrypt” function. It leverages AES 256 encryption for their infection.
Then it will open the target file using the “CreateFile” function and retrieve the size of the target file using “GetFileSize”. After this the malware will decrypt different file extensions and check if the file extension of the targeted file is in the list.
Conti ransomware will not just encrypt the files of the infected machine but also spreads and infects the other machine on the same network using SMB protocol.
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