bleepingcomputer.com - Cybersecurity firm Profero cracked the encryption of the DarkBit ransomware gang's encryptors, allowing them to recover a victim's files for free without paying a ransom.
This occurred in 2023 during an incident response handled by Profero experts, who were brought in to investigate a ransomware attack on one of their clients, which had encrypted multiple VMware ESXi servers.
The timing of the cyberattack suggests that it was in retaliation for the 2023 drone strikes in Iran that targeted an ammunition factory belonging to the Iranian Defence Ministry.
In the ransomware attack, the threat actors claimed to be from DarkBit, who previously posed as pro-Iranian hacktivists, targeting educational institutes in Israel. The attackers included anti-Israel statements in their ransom notes, demanding ransom payments of 80 Bitcoin.
Israel's National Cyber Command linked DarkBit attacks to the Iranian state-sponsored APT hacking group known as MuddyWater, who have a history of conducting cyberespionage attacks.
In the case investigated by Profero, the attackers did not engage in ransom payment negotiations, but instead appeared to be more interested in causing operational disruption.
Instead, the attackers launched an influence campaign to maximize reputational damage to the victim, which is a tactic associated with nation-state actors posing as hacktivists.
Decrypting DarkBit
At the time of the attack, no decryptor existed for DarkBit ransomware, so Profero researchers decided to analyze the malware for potential weaknesses.
DarkBit uses a unique AES-128-CBC key and Initialization Vector (IV) generated at runtime for each file, encrypted with RSA-2048, and appended to the locked file.
Profero found that the key generation method used by DarkBit is low entropy. When combined with the encryption timestamp, which can be inferred from file modification times, the total keyspace is reduced to a few billion possibilities.
Moreover, they found that Virtual Machine Disk (VMDK) files on ESXi servers have known header bytes, so they only had to brute force the first 16 bytes to see if the header matched, instead of the entire file.
Profero built a tool to try all possible seeds, generate candidate key/IV pairs, and check against VMDK headers, which they ran in a high-performance computing environment, recovering valid decryption keys.
In parallel, the researchers discovered that much of the VMDK file content hadn't been impacted by DarkBit's intermittent encryption, as those files are sparse and many encrypted chunks fall onto empty space.
This allowed them to retrieve significant amounts of valuable data without having to decrypt it by brute-forcing keys.
"As we began to work on speeding up our brute force, one of our engineers/team members? had an interesting idea," explained Profero.
"VMDK files are sparse, which means they are mostly empty, and therefore, the chunks encrypted by the ransomware in each file are also mostly empty. Statistically, most files contained within the VMDK filesystems won't be encrypted, and most files inside these file systems were anyways not relevant to us/our task/our investigation."
"So, we realized we could walk the file system to extract what was left of the internal VMDK filesystems... and it worked! Most of the files we needed could simply be recovered without decryption."
The Kaspersky GERT has detected a VBS script that has been abusing Microsoft Windows features by modifying the system to lower the defenses and using the local MS BitLocker utility to encrypt entire drives and demand a ransom.
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Useful quantum computers aren’t a reality—yet. But in one of the biggest deployments of post-quantum encryption so far, Apple is bringing the technology to iMessage.
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Here's an article from a French anarchist describing how his (encrypted) laptop was seized after he was arrested, and material from the encrypted partition has since been entered as evidence against him. His encryption password was supposedly greater than 20 characters and included a mixture of cases, numbers, and punctuation, so in the absence of any sort of opsec failures this implies that even relatively complex passwords can now be brute forced, and we should be transitioning to even more secure passphrases.
Or does it? Let's go into what LUKS is doing in the first place. The actual data is typically encrypted with AES, an extremely popular and well-tested encryption algorithm. AES has no known major weaknesses and is not considered to be practically brute-forceable - at least, assuming you have a random key. Unfortunately it's not really practical to ask a user to type in 128 bits of binary every time they want to unlock their drive, so another approach has to be taken.