According to Bleeping Computer, Advanced Intel’s Vitali Kremez analyzed Conti and found ransomware based off the code for Ryuk, another crypto-malware family. He also discovered that Conti was using the same ransom note template that early versions of Ryuk employed in their attack campaigns. Finally, Kremez revealed that Conti appeared to be using the same TrickBot infrastructure as Ryuk for its ransomware attack campaigns.
The security researcher didn’t go as far to say that Conti was the direct successor to Ryuk. However, he did cite ID-Ransomware data as supporting evidence. He specifically pointed to the fact that submissions of Conti to the service had increased at a time when reports involving Ryuk were on the decline.
A Look Inside Conti’s Functionality
Carbon Black’s Threat Analysis Unit (TAU) researchers found a digital threat in Conti that in many ways behaved like a standard ransomware family. The sample they analyzed iterated files on the local system and on remote Server Message Block (SMB) network shares. Ultimately, it leveraged AES-256 via a hard-coded public key to perform its encryption routine.
But, TAU found some important characteristics that set Conti apart from other modern ransomware. First, researchers observed the ransomware family employs several different anti-analysis methods. These techniques include applying a string coding routine to nearly every string text of the malware. As a result, Conti hides the Windows APIs it needs to use for its infection chain.
Second, the ransomware arrives with command-line abilities that enables it to encrypt specific IP addresses. Such a capability imbues those in control of Conti with the power to conduct targeted attacks, while monitoring a victim’s network (Malicious actors could still use Conti to encrypt the entire local drive and SMB network shares automatically, however.). As such, the ransomware could use that tactic to reduce the “noise” of an infection, helping it to further foil analysts’ work.
Even so, the Conti sample observed by TAU was noisy in other ways. Indeed, researchers observed the ransomware using vssadmin to ensure the deletion of the Windows Shadow Volume Copies. This prevents a victim from restoring their data on their own. The analysts also witnessed the ransomware execute 146 individual commands designed to stop potential Windows commands before it proceeded with its encryption routine.
Last but not least, TAU discovered that Conti employed the Windows Restart Manager to unlock files to ensure they were open to encryption. In doing so, it ensured it could cause the maximum amount of damage.
The Significance of TrickBot to Ryuk (and Now Conti)
Ryuk’s relationship with TrickBot’s infrastructure goes back to the beginning of 2019. In April of that year, Cybereason reported on a “triple threat” infection chain in which a phishing campaign used a weaponized document to install Emotet. It’s at that point when Emotet downloaded TrickBot, malware that ultimately invoked its own downloader capabilities to drop a Ryuk payload on the infected machine.
More than a year later, researchers are still working to understand the relationship between TrickBot and Ryuk. SentinelOne revealed its own analysis of several attack campaigns involving both digital threats in June 2020. The security firm’s work uncovered that the attack operations waited approximately two weeks between the time of the initial TrickBot infection and the deployment of Ryuk.
How to Defend Against a Conti Ransomware Infection
Security professionals can help defend their organizations against a Conti ransomware infection by using relevance scoring to make their threat intelligence more actionable. This will ensure they’re paying attention to emerging threats, including Conti, that pose the greatest threat to their organizations. They can then use that intelligence to prioritize their security efforts accordingly. Given the evasive nature of Conti, security professionals should also ensure they have a robust data backup strategy so they can recover their files in the event of an infection.
David Bisson is an infosec news junkie and security journalist. He works as Contributing Editor for Graham Cluley Security News and Associate Editor for Trip...