Sophos Discovers New Memento Ransomware
OXFORD, United Kingdom, Nov. 18, 2021 (GLOBE NEWSWIRE) -- Sophos, a global leader in next-generation cybersecurity, has released details of a new Python ransomware called Memento. The research, “New Ransomware Actor Uses Password Protected Archives to Bypass Encryption Protection,” describes the attack, which locks files in a password-protected archive if the Memento ransomware can’t encrypt the targeted data.
“Human-led ransomware attacks in the real world are rarely clear cut and linear,” said Sean Gallagher, senior threat researcher at Sophos. “Attackers seize opportunities when they find them or make mistakes, and then change tactics ‘on-the-fly.’ If they can make it into a target’s network, they won’t want to leave empty handed. The Memento attack is a good example of this, and it serves as a critical reminder to use defense-in-depth security. Being able to detect ransomware and attempted encryption is vital, but it’s also important to have security technologies that can alert IT managers to other, unexpected, activity such as lateral movement.”
Sophos researchers believe the Memento operators breached the target’s network in mid-April 2021. The attackers exploited a flaw in VMware’s vSphere, an internet facing cloud computing virtualization tool, to gain a foothold on a server. The forensic evidence Sophos researchers found indicates the attackers started the main intrusion in early May 2021.
The attackers used the early months for lateral movement and reconnaissance, using the Remote Desktop Protocol (RDP), NMAP network scanner, Advanced Port Scanner, and Plink Secure Shell (SSH) tunneling tool to set up an interactive connection with the breached server. The attackers also used mimikatz to harvest account credentials to use in later stages of the attack.
According to Sophos researchers, on Oct. 20, 2021, the attackers used the legitimate tool WinRAR to compress a collection of files and exfiltrate them via RDP.
Release of the Ransomware
The attacker first deployed the ransomware on Oct. 23, 2021. Sophos researchers found that the attackers initially tried to directly encrypt files, but security measures blocked this attempt. The attackers then changed tactics, re-tooled and re-deployed the ransomware. They copied unencrypted files into password-protected archives using a renamed free version of WinRaR, before encrypting the password and deleting the original files.
The attackers demanded a ransom of $1 million in bitcoin in order to restore the files. Fortunately, the target was able to recover data without the involvement of the attackers.
Open Entry Points Let in Additional Attackers
While the Memento attackers were in the target’s network, two different attackers broke in via the same vulnerable access point, using similar exploits. These attackers each dropped cryptocurrency miners onto the same compromised server. One of them installed an XMR cryptominer on May 18, while the other installed an XMRig cryptominer on Sept. 8 and again on Oct. 3.
“We’ve seen this repeatedly – when internet-facing vulnerabilities become public and go unpatched, multiple attackers will quickly exploit them. The longer vulnerabilities go unmitigated, the more attackers they attract,” said Gallagher. “Cybercriminals are continuously scanning the internet for vulnerable online entry points, and they don’t wait in line when they find one. Being breached by multiple attackers compounds disruption and recovery time for victims. It also makes it harder for forensic investigations to unpick and resolve who did what, which is important intelligence for threat responders to collect to help organizations prevent additional repeat attacks.”
Sophos believes this incident, where multiple attackers exploited a single unpatched server exposed to the internet, highlights the importance of quickly applying patches and checking with third-party integrators, contract developers or service providers about their software security.
Sophos also recommends the following general best practices to help defend against ransomware and related cyberattacks:
At a Strategic Level
Sophos endpoint products, such as Intercept X, protect users by detecting the actions and behaviors of ransomware and other attacks. The act of attempting to encrypt files is blocked by the CryptoGuard feature. Integrated endpoint detection and response, including Sophos Extended Detection and Response (XDR), can help capture nefarious activities, such as when attackers create password-protected archives like those used in the Memento ransomware attack.
Contact info: Samantha Powers [email protected]
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